I think you are asking if you can change the gearing on your bike to make it easier to climb. The short answer is yes, this is possible for most geared bicycles, but it depends on the type of bicycle that you have.

If you have a bike with an internal geared hub (IGH), this is generally not possible. This type of bike does not have exposed derailleurs, the gears are all inside the rear wheel hub. Perhaps you can look for a compatible IGH with lower (easier) gears and build up a wheel, but I don't know if this is possible. Sorry, I'm not familiar with IGH bikes.

If you have a bike with derailleur shifters, then you can usually get a new cassette (or possibly free wheel for older bikes) - this is the cluster of cogs on the rear wheel - with lower gears. It would be a good idea to go to your local bike shop (lbs) for advice on the correct cassette/free wheel. There is a limit on the size of the largest cog that depends on the type of rear derailleur that you have. Also, the cassette or free wheel must be compatible with your rear hub. (edit: you will probably also need to add one or more links to your chain.)
You can also, in some instances, get easier gears by going with smaller chain ring(s) in front, but this is often more complicated, because it may require you to (a) get new chain ring(s) - if you have multiple chainrings and you change the size of the smallest ring to get lower gears, you may also have to get smaller ring(s) for the larger one(s) because there is a limit on the difference in the number of teeth between chainrings that your front derailleur can handle; (b) change the height of the front derailleur (not always easy if you have a braze-on derailleur mount, though there are adapters that you can buy if you need to get your front derailleur lower than is allowed by your braze-on mount); or possibly even (c) get a new crank if the crank spider will not accept a smaller chainring.
Your best bet, as I said above, is to go to your bike shop for advice.

If you have a single-speed or fixed gear bike (you only have one gear), then of course you can get a larger cog for the back or a smaller ring for the front (however, it must be compatible with your crank spider), and you'll only have to add/remove chain link(s) and/or move the rear wheel in the dropouts.

If you have a very inexpensive bike (for example, branded by a large department store or, in the U.S./Canada anyway, sometimes a gas station chain) then often the parts to do what you're intending to do are difficult to find or don't exist, so it may be better to just replace that bike with a new one with the gearing that you need.

I hope that this helps.