Chloesowner,
Your second signature nobody can see. Why don't you remove it from your signature? Go to user cp and you can erase it there.
After you have finished that:
You make a custom avatar, right click on finished picture, click "save picture as" and save it into my pictures or wherever you want.
Then go into your user cp.
Go to edit avatar.
To change your avatar click browse, look for the picture you already saved in "my pictures"
Double click it
Then go to the bottom of page and click "save changes" or whatever it says.
That should be about it.