Use the WASD keys to control the owl - W for forward and up, S forward and down (pitch) and A left, D right (yaw). This way you can easily avoid obstacles. The mouse is only for camera view - move it to see around you. Slide your mouse slightly up to go upwards more, slightly backwards to go downwards. When your owl's flying it tells you on-screen how to select and drop bombs. Do a test run while you're in a camp without enemies. When the owl sees an enemy a left mouse icon will appear so use it to make the owl kill enemies from the air, very silent!
When you first start the game and have established where base camp is, talk to people there to upgrade Takkar's, Sayla's, Tansay's huts and don't start out in the world fighting too early. You won't be strong enough and building these huts gives you the skills of the owner so you become stronger. Use your Reward Stash to start building these huts, the contents are not just for your own use. On your travels in the world, pick ingredients, kill to skin animals for fat and hide and meat (for your tamed companion animal later in the game). All this collecting resources is worth it in the long run when you will have what you need already when quests are given.
Unlock Skills using K whenever possible. Especially under Survival Skills / the Primitive Takedown because then you can creep up behind enemies, use F and kill them without even having to fight. That will help you a lot. Take it all gradually.
It is difficult to find anything about the owl's controls online, hence this post. Hope this helps.