How do you add an avatar fo your profile pic?

I'm having trouble doing this. I'm trying to upload my countrys flag as my pic, and for some reason I'm having a hard time....? like i go through all the steps, i upload the pic...then crop it...and after i do those steps is when i have a hard time. it brings me to an option of using the image which is up now ofthe blue pic with the exclamation point, rather than the pic i want....why is this? am I doing something wrong?