In VIPER you can add destinations under the "Destinations" tab in the main header. Clicking on the "Destinations" tab shows you all destinations for your DMC arranged by Region first, with Destinations under that. You can set up regions for your needs, whether they are different countries, states, etc.
Add a Region by clicking on the "Add a Region" button at the top of the page, and add a destination to a region by clicking on the "Add a Destination" button underneath a specific region.
You can also view hotels for a specific destination by clicking on the "Hotels" button to the right of each destination.