So here are a few steps in how to setup the create user action.

1. Download and install the plugin via the plugin repository or manually via this url.
2. After the install go to your page where you want to setup the create user form.
3. Insert the form and setup all fields as usual. Be sure your field contains: First name, last name, email and a password field. Also change the ID of these field to something easy to manage for example “firstname” “lastname”.
4. In the menu Action after submit select the “Create user” action.
5. Now the Create user tab appears. Open this tab.
6. Here you see some input fields. In all these fields we need to set the form field ID we set in step 3. It will be something easy like “name” and “email” or when setting a new field it defaults to something like “field_7c6e5bb” enter all these fields here. 
7. After setting up all these fields click update and you are all set. When a user submits the form they will create a user with the subscriber role with that data.