(I'm sorry if this is in the wrong forum again. You guys don't exactly make it easy to post where to get help from since it seems like everyone here KNOWS what they're doing x.x)

A friend of mine made a sprite for me and I imported it into RPG Maker, but he doesn't move. He turns up, left, right, and down but that's all he can do; he doesn't walk anywhere? How do I solve this problem? Does it have to do with the canvas size? Please help!

Um... Well, I'm 99% sure it's not the sprite causing the problem. The sprite size has no affect on collisions. I would check the passability of the tile your walking on, and make sure it's set to a "O".

The tile is marked under O.

May we have an image of this?
I'm not sure what you mean, really. You went from a sprite to tile

I used the Kaduki sprite template (I forgot the artist's name ^^; ) and a friend of mine edited. I think it has something to do with the canvas size but I don't know what exact size to set it at.

If it's just the one character, make sure you put a "$" before the name. This will ensure it's playability.
I.E: $Untitled.png

*facepalm* I found the problem. It's not the sprite, it's the tilesets I downloaded. Sorry about that. I guess I'll just have to work with the tilesets given to me before going back and fixing the problem with the other tilesets. Sorry everyone!