There are two methods to activate your license key.

Method 1

1. Go to WP Dashboard >Plugins and find the Plugin Elements for LifterLMS.
2. Below the name of the plugin, click the link – Activate License.
3. Now a box will be opened. Put your license key and click on the Activate License button.

And you are done.

Method 2

1. Go to WP Dashboard > Elements for LifterLMS Settings page > Account and at the bottom of the page, click on Activate License Button.
2. Put your license key in the box, and click Activate.

And you are done.