Hello, my character keeps falling through the floor 
Hey OnSic, you are posting in the wrong section, this is the second time, you probably want to ask in the unity support forum. That said, there could be a few reasons your character is falling through the floor, your character, and the “floor” both need to have collidors on them, otherwise gravity doing its thing will make your character fall 
How do i add collidors to the character ?
(and sorry for posting in the wrong section)
Well, the easiest way is to select it, and on the import, select generate collidor. This is probably not super ideal for your character tho. But its a start. If your using one of unity’s prefabs, character controller, or third person character controller, they both have collidors by default. So make sure your floor has one. By default, unity’s primitives should have them as well, but occasionally moving them around the scene, you might separate the collidor from the object (green select is collidor, blue selection is the mesh)
Okay thanks
but i’ve imported the robot that comes with unity, but when i try adding the walk and run animation the character won’t “use” it, what am i doing wrong ?
Not sure which robot, but, I would suggest checking out the Lerpz tutorial on unity’s website - just go to the main page and follow the links to the tutorial section, this will answer a lot of questions for you in regards to importing things into unity, setting up animations, and other things that haven’t quite come up yet. Good luck.
Thanks a lot