You have probably arrived here from a photographer's portfolio. Prism Portfolio is a personal showcase for photographers whose camera club uses Prism - the photographs are already in the system, so publishing a page is a matter of choosing and arranging, not uploading all over again.
The answer is different depending on whether your club already uses Prism.
Then you already have a portfolio waiting - it just has not been published yet. Sign in as you normally would, open My Portfolio from your account, choose your photographs, and publish when you are happy with it. It stays a draft until you say otherwise.
If you are not sure whether your club uses Prism, or you have never signed in, ask your club's competition secretary. They can send you an invitation.
Signing in does not create a club membership. Only your club can add you as a member.
You do not need a camera club. Create an account, confirm your email, and you have your own portfolio at prismphoto.club/p/yourname.
The founding offer
An independent account has your images and your portfolio, and nothing club-related: no competitions, judging or member lists. Nothing will be deleted or unpublished without us telling you first. If your club uses Prism, a portfolio is already included in your membership and this does not apply to you.
Portfolios are one part of Prism. The rest of it runs competitions - entries, judging nights, member voting, season standings, external competitions and the club programme.
See Prism for photography clubs