You have not stated the drive train gearing or the hills you want to climb. Gearing is probably the only place you could change on the bike if it is geared too high.
Rear cassettes will take you from 11 to 50+ in 12 speeds if you want to go that way. A smaller front chainring may be a less drastic change. On the other hand, you can gear the bike so low that your cadence becomes a limiting factor on going fast enough to balance the bike. A lot of people start walking if they cannot bike faster than 2 MPH. The slower you can ride, the steeper your cardio system can climb. If your legs are the limiting factor, you need a lower gear or better legs.
Training is probably your best bet. I ask my friend who does a lot of long climbing rides. He told me that it does not take long to get in shape if you ride 30 or 40 miles before breakfast and work 3 days a week. After about 3 days, you start to lose what you have gained. You may want to get your legs and cardio in shape on relatively flat rides before you go back to climbing. To get good at climbing, you have to do it. I am a flatlander with my highest climb, just under 1000 feet. Riding 10 to 30 miles at a constant speed multiple times a week is long slow training. It is surprising how fast the speed can build if you do it a few times a week.