It sends a validation email so check your email, make a disposable one somewhere if you want (Outlook.com, Yahoo, etc). Be sure to check your spam folder too.
Pick any picture and upload it / choose it as your avatar icon. It doesn't need to be of you, just can't be inappropriate. This step is necessary to weed out spam accounts.
If you don't have a picture just google or bing something right click save, then upload.