If you are coming from the Plugins screen, you need to click on the Activate button on the Hospitality for Quick Serve and Fine Dining plugin tile to activate the plugin.
From Manage Account Section:
If you are coming from the Manage Account section, you need to navigate to Choose My Subscription section and put a tick in the activation checkbox to mark the Hospitality for Quick Serve and Fine Dining plugin as Active.
Plugins in Tagrain are either Subscription Based or License Based. So the price that you pay for your plugins is based on the number of POS terminals that you have in your setup and the number of licences that you have acquired.
Activating or Deactivating this Hospitality for Quick Serve and Fine Dining plugin will not affect your subscription amount for your next billing cycle because the plugin is free.