You have 2 broad options.
You can use a service such as proboards, who will do most of the hard work for you.
Or if you have some IT skills (or someone in your community does), the key steps to DIY are:
- get familiar with running a forum, plenty written on the web about this
- pick an available domain name and put together a basic plan for your community, including your budget, theme, rules etc
- look at the available forum software (such as SMF which runs this site and is free, or vBulletin which is widely used but has a charge etc)
- look around for web hosting companies that will support the forum you picked
-- ring the host and ask if they support vBulletin, SMF
-- check that they are in your budget
-- look for one that lets you start small and grow to a bigger hosting plan as the site grows
- register domain and signup with the webhost company to host it
- install forum software on your site
- modify and theme your forum to suit your community (alternatively pay for theme to be created just for you)
- start promoting the forum within your community
Goose