You can add as many cities as you wish. Go to the Settings tab, open the Location section.
You can either search a city by name, or use the GPS sensor of the device to locate your current position, which you can decide to bookmark for future reuse.
If you choose to Locate using the GPS, you will first be prompted to double-check that your current place isn’t already in your list of bookmarks, and if not, you may click the blue button at the bottom of the list.
From the Date screen (leftmost tab), you can swipe the city name left or right (on iOS) to jump to the next bookmark.