This addon allows you to create a registration form for a particular membership level on any post or page.
You can use it to give access to various different membership levels for free.
You will be able to select a membership level from the dropdown and it will generate a registration form shortcode for that level.
After you install this addon, go to the “Form Shortcode” menu from the admin dashboard to use it. More details here
This addon requires the Simple Membership Plugin.