Welp, first step to getting to the terminal, as you imagine, is clicking sandbox in reassembly!
The magical thing that I call a terminal sits on the up left corner of your screen!
QUICK TIP: press [ and ] to shrink and expand the terminal window!

Anyways, on to how to use sandbox like a brain-damaged potato!
All this stuff will seem complicated, but you will get used to it!

-Double-click on empty space to set your blue marker/cursor where things will happen from the commands in terminal

-double click on a ship to select it

-single clicking will only select a single block

-shift-drag to select a bunch of things at once

-shift click to select more things and unselect them too!

-1 to command a selected ship

-3 to go into build mode where you can do all this stuff

-2 for command mode, where the game draws a bounding box, the ship's core radius, and the ship's bounding radius around selected ships. You can also left-click to make selected ships fly there.

- v to hide/show the ui elements(also known as hud)

- esc to act like you are in the actual game

- \ to get out of game mode

- shift+] to slow down time

-shift+[ to speed up time

-p to freeze time (kinda buggy so just for deleting/copy pasting things, not good for building)

There are an ungodly amount of things you can do with terminal, so here's the simple ones!

Usage: help
EX: help

This will show you all the things you can do, but It won't necessary show you how, so that's why I still made this guide.

Usage: ssave <shipname>
EX: ssave chimigangaship

This saves a ship. For example, If I made a ship with Terran command(ship will be saved to the ships of your original command module's faction), and typed this, A new ship file called 8_chimigangaship.lua would appear in the base game ships.lua, and now would appear in-game.
I would not recommend this, however, because this modifies your actually game and will be hard to find and get rid of.

Usage: sopen <faction number>_<shipname>
EX: sopen 8_chimigangaship

This example builds off of our earlier ssave, and what this does is spawn in our saved ship at your blue marker. Note that since our saved ship was Terran, and Terran's faction number is 8, we put 8 before the ship name, and also an underscore. I recommend doing this after saving a ship, to check if your ship's bindingID's aren't screwed up. If they are, set them manually by double clicking on the ship, pressing 1, and then b. If they get screwed up no matter what, and you do not know how to use your computer's terminal, then you will have to find the ship file and fix them yourselves, unfortunately. If you do know how to use your computer's terminal, you're in luck! Open the reassembly folder in library (or saved games, on windows) in file browser/finder/whatever, and throw the file[from here: [url=https://repl.it/talk/share/shipautocorrector/57351]https://repl.it/talk/share/shipautocorrector/57351[/url]] into the ships folder, and then run it from terminal[the computer one, not reassembly's] and it will explain from there! (what it does is fix ssave's messing up bindingId's)!

Usage: heal
EX: heal

This will heal your selected ship/station/(anything with a command block and one other block) to 100% hp on all blocks!

Usage: target <blocks> <hp per block> <shield>
EX: target 100 100

this will spawn a target at your blue marker, with a specified number of blocks and hp per block, and also shield but it seems to not care what the shield number is set to.

Usage: activate
EX: activate

this will activate your selected ship, and it will now act as if it was in campaign(the normal game, I mean). It also means that the ship will regenerate destroyed blocks. ssaving a ship also activates a ship.

Usage: deactivate
EX: deactivate

Just turns your selected ship into a veggie. Also stops the block regen of a ship.

Usage: palette <faction number>
EX: pallete 8

This spawns all blocks at your blue marker, EVERY SINGLE BLOCK from a specified faction.

Usage: minpalette <faction number>
EX: minpalette 8

This is much like palette, except it only spawns the first block from each group. (if not you are a modder, it basically spawns only the first scale of square from the Terran faction, for example.)
I usually recommend palette for modding, as you know what blocks are missing.

Usage: level_save -f
EX: level_save -f

I'm not really sure how this works, but it sets your default sandbox to everything it has now, meaning every time you open sandbox you will see these things on your screen instead of the 'once there was a command line' text!

Usage: fleetpalette <faction number>
Ex: fleetpalette 8

this spawns all ship designs from a specified faction at the blue cursor, very useful in modding to get that feel of your ship designs.

Another thing to note, you don't have to finish typing the command. For example, you can just type 'act' to run the activate command and it will auto-fill. Additionally, you can press TAB to see all possible commands starting with whatever you type. This is especially useful if you have mods that have long complex IDs. You just type the first few numbers and hit TAB. (also works with the faction name) -Joyus18

More stuff will be added, just wait!

You probably don't care, but thanks for reading and have a great day!

Credits:
-joyous18
-Debris Field