Manually add them. Go to the setup menu and select users. Then click add, fill out the required information and click save. This will send the user an invite to your SWGT Guild site.
Enable registration. Have a super user of your SWGT Guild site enable registration on the site setup. Go to the setup menu and select site setup. Then scroll to the "general settings" section and toggle "allow registration" to "yes" and click save.
Then you can give the URL to your SWGT Guild site to whomever you want to have an account, they can register themselves and then you will need to "approve" the registration request. Go to setup menu and select users. You will then select "pending users" and you will need to follow the approval workflow. There is also a homepage tile for "Pending Users".
From a security prospective, option 2 above is the most secure as super admins do not need to know usernames and email addresses for each guild member whom needs access.
