In case it isn't clear, in order to add the DLC to the game you'll need to do the following:
- Either on the Home Screen or in 'My games & apps' once your cursor is on Civ 7 click the Xbox button (the lit up circle on your controller with the X on it).
- Scroll down to the 'Manage game and add-ons' option and select it and press A.
- On the right you'll see three options; the Civ 7 game, updates, and saved date. The game should already be highlighted. Select it and press A.
- This will list all the downloadable add-ons. You can either scroll through and select the ones you want, or you can select the 'Select All' option on the right and then select the 'Save Changes' button. This should start the installation process.