How do I import an avatar?

I have found lots of web pages with free avatars, then download them to my computer.  However, when I try to download, it tells me it is not the right format/pixel size.  I have tried at least ten times.  While  not a genius, I am generally not the slow kid in class.  Just can't quite figure it out.   Help, anybody?  Thanks.

The avatar has to be 100x100 pixels or less in size (pretty small).
And it cannot be over 20k in total size.

You can go here and select avatars by size and dimension
avatar.hq-picture.com/funny-n-scary-avatar-39918.html

- you can also create your own by re-sizing them on different websites (or with programs on your mac/pc).

Good luck!

J