Premium karmas are unique type of karma action you can do on the Instantgo app. As you see the different types of karmas, you will see that some of them are premium. They require a defined set of points to use them a single time.
Each time you click on a premium karma, you will see on your scree a definition of what makes that karma special and see if you want to use it.
Regarding karma points, you can earn them doing several actions on the app or simply buy more points at anytime.