Opportunity Profile Tab
In your Opportunity Profile, there is a tab labeled "Sign-In." Here you will find a list of all the "Stations" you put in the "Sign-In Setup Options" page. Here you can specify which "Stations" volunteers can use to sign-in for this Opportunity.
The "Sign-In" tab will only appear on accounts that you enabled sign-in. The "Profile" tab is also referred to as the work area.