PSDProject is a mail invitation-based system.
When you receive the mail  invitation, then you can participate.

1: Photoshop it and continue freely while respecting the size (800x800 pixels, click to enlarge image), resolution (300dpi), and compression (JPG, maximum quality).

2: Send it!  HERE

3: Mail your next photoshop artist friend, send the JPG and ask him or her to continue the PSDProject.