Press the button to turn into a mouse
Go up to the mouse trap on the ground and press E to eat the cheese

You can do this 2 ways

Using the camera and toilet paper, build a ladder on top of the red clocks up to the top of the desk
Turn into a mouse using the button
Climb up to the desk
Press the button on the desk and jump down into the floor
Go forward and to the left into the mouse hole
Select "am mouse"
E to Eat the cheese

OR

Get on the desk
Press the button on the desk
From the bed, press the button into turn a mouse
Jump into the floor
Go forward and to the left into the mouse hole
Select "am mouse"
E to Eat the cheese

Press the button on the desk
Go through the floor
Walk all the way forward into the darkness
Prepare
Don't get jump scared like I did

Put the toilet paper on the floor
Climb on the desk and press the button
Go on the bed
Press the button to turn into a mouse
(it's easiest to get as close to the end as you can, jump, and press the button)
Take the toilet paper, walk forward and left into the mouse hole
Put the toilet paper onto the X
Walk out of the X area and then back in as the door is closing

Put the toilet paper on the floor
Get on the desk
Press the button
Go onto the bed jump and press the button to turn into a mouse
Hold the toilet paper upright to hide behind it
Walk into the darkness and get behind "???"
Go into the mouse hole behind "???"
Read the note on the ground

Get on the desk and press the button
Go to the edge of the bed jump and turn into a mouse
Walk forward and left into the mouse hole
Select "am human"
Pick up the sticks and put them down a bunch until you get the achievement