The phpBB2 mod that attached that to our forum does not work with phpBB3, for which we just upgraded.
Look at the sub-forums located above this forum's index for places to upload skins now. See here
for an example on what information to include.
When we get caught up, we'll get something posted that explains the process a little better. Essentially now, though, skins can be uploaded to the forum as attachments.