Need help understanding my grip shifters on my handle bar
You have two shifters. A friction shifter for the front derailer and a 6-speed indexed shifter for the rear derailer.
The shifters are operating by turning the grip front and back (like a motorbike throttle).
The front shifter is on the left. You must learn how to find the right position yourself, because it is a friction shifter, you can move it continuously. After the gear is shifted you must yourself find the position that does not make any bad noise.
The rear shifter is on the right side. There are 6 predefined positions for those 6 speeds, that means 6 different sprockets, chainwheels, at the rear derailleur.
You turn the right/rear shifter towards you to shift to an easier gear/larger cog in the rear.
You turn the right/rear shifter away from you to shift to a harder gear/smaller cog in the rear.
You turn the left/front shifter towards you to shift to a harder gear/larger cog at the front.
You turn the left/front shifter away from you to shift to an easier gear/smaller cog at the front.
If you want to look on the numbers, then the smaller the number indicated, the easier gear is selected.
The gear is not changed immediately, you must turn the cranks that hold the pedals first after operating the shifter. Do not push too hard or the chain can fall or get jammed.
To go uphill, you normally go slower, so you select a smaller chainwheel at the front and a larger chainwheel at the rear. That way you can go push with a reasonable force even if you go slower.
When you want to go fast on a flat or downhill, you select a larger wheel in the front and a smaller wheel at the rear. That way you do not have to turn your pedals too fast.
Do not select the smallest cogs on both sides at the same sides or the largest cogs on both sides at the same time. That is called cross-chaining  and is bad for the drivetrain and will likely be noisy.
As others noted, you should try to change the front gear less often and the rear gear more often. But everyone develops some personal style of shifting after some time. It is important to adjust your shifting to avoid those bad habits that lead to fallen or jammed chains. Especially, do not shift under load. The cheaper the drivetrain is, the worse it copes with bad shifting. Expensive derailers can shift multiple gears at a time, but try to avoid it with yours.