One way to make your bike more hill-friendly is to change the size of the large cogwheels the chain runs on, often called 'chain rings', at the front between the pedals, and 'sprockets', at the back by the rear wheel axle.

If you only have one sprocket at the back because you have an internal gear hub (IGH) or a single-speed bike, you can easily replace it with a larger one. However, if you have a cluster of 7-10 sprockets at the back, because you have derailleur gears, then it might be easier to replace a front chain ring (front sprocket) with a smaller one to achieve the same effect. In both cases you end up with a lower gear range that makes it easier to go up a steep hill.