After you connect a Google account, some locations may appear grayed out. Gray means the location is disabled: it sits in your account but is not synced or tracked, and it does not count against your plan until you enable it.
Enabling a location
There are three ways to enable one:
From the Locations list, open the three-dots menu on the right of the location and switch on Enable location.
Open the location, and use the enable option on its page.
Open Google Accounts (from the menu under your email, top right), select the Google account, and toggle the location on there. This view is handy for enabling several locations from one account at once.
Enabling a location counts it against your plan's location allowance. See Connecting Your Google Account & Adding Locations.