the Amateur Photographic Exchange Club's
You'll need a camera and a viewer. You'll take prints or slides. (If you use a 1950s era stereo camera you may decide to take mostly slides and have occasional prints made from your best work.)
You'll use modern 35 mm slide or print film.
SLIDES: You'll send your slides to a neighborhood lab and cut and mount them yourself in two-stereo-halves-in-one-cardboard-frame mounts you'll buy from a 3D specialty mail-order house.
PRINTS: How you handle prints will depend of the film format you use. If you use a standard modern "8p" camera, you'll have your prints developed at a neighbourhood lab. If you use a non-standard "4p," "5p," or "7p" format (more about this in Stereoscopes and cameras), you'll make friends with a local semi-pro lab an pay them extra to make non-standard sized prints. No matter what print format you use, you'll trim and mount your prints yourself.
You'll look at your slides with a stereo slide viewer. You'll look at your prints with a stereoscope, a lorgnette, or a View-Magic viewer.
Stereo photography is a hands-on hobby. From the 1950s into the early 1980s you could take 3D photos with a special-purpose camera, drop your film off at a local lab that did 3D processing and mounting, and look at your pictures in an off the shelf 3D viewer. Nowadays you'll have to improvise a camera, search for a lab, mount your slides and prints yourself, and buy a viewer from a niche mail-order supplier. All that is just part of the process. Think of it as part of the fun.