The Custom Form Tool has 7 pre-made "actions" that you as the user can set to happen when the submit button is hit and the form is submitted.
In this section, we will take a look at the "Create a User" Action: This action is primarily used if you have a sign in tool and want to allow users to fill out a form for the purpose of creating their own usernames. This rule will allow simply clicking the submit button to automatically add the new user to an existing user group, thus, saving you the time of having to go in and add the user manually based on the data that they send you.
First, create the form for the user to fill out:
NOTE: Make sure to include a username/password field instead of the normal text field. It gives access to many more options and features for user management. Like so:
Next, fill out the Edit Actions tab for "Creating a User" and assign the each section to the proper field that corresponds in the custom form:
Once this is done, have the user fill out the form, hit submit, and BAM: