An account with our Gallery is sufficient, which I saw you do have already. If you forgot your password let me know, I can reset it. Photo uploading and linking in the forum postings functions basically the same way as with all the internet services.
Forum admins do not like these photo services much. The picture link sooner or later breaks, and the pic is gone. For photos which are relevant for the posting it is much preferred using the Gallery. The only person who can break picture links there is me, and that is bad enough already
If you need help with the handling the process, just let me know.