Licensing page of Gallery Master gives an idea about the Activation Process.
This page consists of screenshots from the Licensing Screen in Gallery Master WordPress Plugin.
Once you have completed the Activation step of the Plugin, click on the “Gallery Master Menu” from “WordPress Dashboard Menu” located on the left hand side of WordPress Page.
This will redirect you to the “Licensing” page.
Here you would need to fill “Order ID” and “API Key” which you have received in an email after purchasing the Plugin along with a download link.
These details will be used for validating the License.