You don't just create them. You'll need an entire membership system to
handle storing users, authenticating logins, etc.. You'll need to start with
determining what sort of server-side scripting your web host supports. They
may not support any, but you need to know what they support before you start
looking at options. Once you figure out what technologies they support you
can start to search on Google for an appropirate membership system. In many
cases, these will also require the ability to run some sort of database to
hold the user information so you'll also need to look into that with your
host as well.
