The first thing to do is to install the Paid Memberships Pro plugin. Note that I'm using the default Twenty Fifteen theme on my site, so I won't be installing another theme. If you'd rather pick a different theme or use your own, you can do so. Follow these steps:
In the WordPress admin, go to Plugins | Add New.
In the search box, type
Paid Memberships Pro
.The Paid Memberships Pro plugin will be shown:
Click on the Install Now button.
When the plugin is installed, click on the Activate link.