where can I change my picture, and what is watermellon?

where can I change my picture?

Also I want to write something about me, but I can't see where can I. Please let me know. also some users have watermellon on next their picture, I wonder how can I get it

In the left menu in your profile you'll see a EDIT button... Is there.
You can put something about you in the button after your translation preferences... Is like: Send a new article... I can't remember.
You can see what the watermelons mean at this topic.
Hugs

Thank you!