First copy your "Magic 2014" folder & paste in the same folder & rename it "Magic 2014 - Modded".
Your Magic 2014 folder is usually located at C:\Program Files (x86)\Steam\steamapps\common\
This is the folder & location you will be running & playing the modded decks on, just so you have your original as a back-up.
So Right Click on the "DotP_D14.exe" or "DotP_D14" & "Send To> Desktop (create shortcut)" this is how you start your modded Magic.

And Yes!, you can still play online from this folder as long as steam is running.

Though if you want to play online with mods, know that all players in a match need to have the exact same mods otherwise the game will either prevent a connection from being established or crash.

"UPDATE ON MULTIPLAYER": http://www.slightlymagic.net/forum/viewtopic.php?f=99&t=16702

You MUST have
WinRAR; Link here:http://www.rarlab.com/download.htm
Or
7zip; Link here: http://www.7-zip.org/download.html
installed to open this pack!!!

Deck Editor & All Files Needed Link: http://s000.tinyupload.com/?file_id=95564672877732653230

Extract the pack to any location, it doesn't matter where.

Also PLEASE Read the "Instructions and Info.pdf" in the pack it will save you a lot of time.

You will also need to copy the d3dx9_43.dll file from the DLL folder in this pack to
C:\Program Files (x86)\Steam\steamapps\common\Magic 2014 - Modded\
folder for the .WAD file to be recognized as a new deck in game.
Now just double click the "DotP 2014 Deck Builder.exe" or "DotP 2014 Deck Builder" & you are on your way to building your very own custom deck!

This guide & pack was put together by Lamron333
DLL File provided by multeyemeteor
Program provided by RiiakShiNal

Original info from these links:

YouTube Video:
Original DLL Link: http://mod.gib.me/dotp2014/d3dx9_43.dll

Original Deck Builder Link: http://www.slightlymagic.net/forum/viewtopic.php?f=99&t=10999

Original page I made into a .pdf for instructions: http://mtg.dragonanime.org/index.php?title=DotP_2014:_Deck_Builder:_Wiki_Doc


Enjoy :)