How to set resolution for android

I am creating android mobile game and i want it to be in portrait mode (height>width) and how do i set it in unity for that. I was playing with unity scavanger project and noticed it has black borders on left and right and that is probably because camera in unity is set in landscape mode and I dont know how to change that.

Also how does resolution change get done in unity. As far as i noticed games dont have that problem but UI have big problems.

Thanks

P.S. I googled all of this and didnt find and good answer that i can understand (if you have link to good explanation i would be thankful)