Toot TOOT, well done. Look forward to seeing your 1st creation. Just remember to save your gimp file to .jpg or .png (I use .jpg) and ensure that image size is under 200k. Then when you are logged on and in the Gallery you should see an "Upload Photos" option appear (in the grey horizontal bar) just about under neath the "Welcome, username" box, select and follow the instructions.
I hope that wasn't too brief in instructions