Can't put in new avatar.....

 I decided to change my avatar to a current picture of me.....since I have always used a pic of multi-colored daisies (for 21months)........then somebody else started using that same avatar......now I can't figure out how to do it......help !   Until I figure it out....I will just be a silhouette.

 http://www.shrinkpictures.com/create-avatar/ 

 Thanks for your help, but it won't let me choose a file???