In the station description view, tap on the star icon over the photo at the top of the screen:

The star will fill in yellow once you have bookmarked the station.

To manage your bookmarked locations, tap on "Bookmarks" on the main menu off the app: 

Tap on the location name to be taken to that station's description:

Tap "SORT" in the upper righthand corner to sort your bookmarks by nearest, date added, or by name: 

To remove a station from your saved bookmarks list, hold your finger down on the station name and swipe left.