To complete the ‘Land on different Bullseyes’ challenge, you simply have to land in specified zones on the map, marked by bullseyes:

They’re very clearly visible even from a high altitude so shouldn’t be too hard to locate, but if you are having trouble, here’s a map from @LootLakeBR showing all of them:

If you’ve done it correctly, confetti will launch into the air when you land and you’ll progress 1 step on the challenge. This has to be done a total of 7 times to earn the reward of 5 Battle Stars.