How do I go aboit doing that?
You will need a fork pump because we are talking about pressures of up to 160psi.
Describing how you do it is difficult in a few words, but I will have a go.
Stand beside the bike and compress the fork by leaning on the handlebars.
Release the compression (lift the bars) slowly.
You want the fork/wheel to remain in firm contact with the ground as you do so.
If it lifts before it's fully extended, the pressure is too low.
There is a knack to doing this, which you can only learn with experience.
A competent bike shop would do it for you, and tell you the pressure they've set.
Still worth buying a pump because the pressure needs to checked every month or six weeks.
In riding, what happens with too low pressure is the fork compresses a little over small bumps, but lacks the pressure to fully rebound.
This happens a few times so you end up running with a near fully compressed fork.
When you hit a bigger bump, you get a jarring sensation because the fork is all but fully compressed already.
So conversely, a higher pressure gives you a more compliant ride.
There is also probably a pre-load adjustment, which relates to your weight.
The instruction manual with the forks should tell you that.