Okay, first you right-click the sprite and select "Copy Image Location". Then, go to "User CP" on the top of the screen, then on the right there will be a thing that says "Edit Avatar." Paste the location on the bar that says "Image URL" and select Okay. You should have the sprite as your avatar.
(And a word of warning, mate. most of the people here are kind of annoyed by misspelling of words on purpose in regular speech. It's fine in /b/uizel, though.)
Hello, Flygon! Welcome to the forums of Victory road! I'm Idno58 and I'm doing this thing where I make sprites for new members, I know you like Flygon, but if you want, can you give me some info as to what else you'd like in the sprite?