The advantage of a trike over a bike when hill climbing is you have no minimum speed.
So you can gear them down a lot lower than a bike, 2-5 gears lower is normal.
The "standard" gearing is around 15"-100", this lets you climb most hills easily.
My first gear is only 9.6" which means 20% hills start to get hard work but I do climb them at ~2 mph.
You need to get used to pedaling with a light pressure on your feet and if it increases due to a hill then drop a gear or more to get the feel back.
The last time I was on an exercise bike and the resistance increased, I went for lower gears ........

The whole idea is to climb the hill while expending as little effort as possible.
Also until you get fit expect to climb most hills in first gear, I know I did.
Then as you get fitter your cadence increases without upping your effort which ups your speed.
Doing that lets you go faster for longer.