Go to "Styles" on top of the phpbb.com website, choose which category your avatar pack/rank or whatever is, then, on the left hand side, click "Add New Link" or something close. Then, fill in the form and Submit and it'll be validated in due time.
Just so y'all know, I have fun making these. =P
No longer supporting phpBB. PM or email me regarding support and you will be ignored. I'm fully done with phpBB and everything.