Frustrated by Avital system in used Prius C 2013

I purchased a used Prius C 2013 with 7000 miles on it, car is basically new.

I have two fobs, the large rectangular one from Prius and a smaller Avital one that is more oval. The dealership neglected to tell me how to use the two fobs and for reasons not worth going into I'm reluctant to pay them a visit.

Car has keyless entry, i.e. gesture entry, which I love. Twice I've tried to alter the settings such that the unlock gesture unlocks all four doors but as soon as I did that, the act of unlocking the car sets off the car alarm like maybe half the time. Understandably it's made me rather gun-shy about using gestures to open the car so I resort to actual pushbutton commands on the Prius fob to unlock the door. This really annoys me. I have never used the Avital fob for any reason, I don't know how it works.

I'd appreciate any advice about reasserting control over the fobs of my car! Thanks.