To measure the wear on your tires and to know when they need replacing, you need to inspect the tread. The tread comes into direct contact with the ground and therefore determines your tire's performance.
A tire needs to be replaced when the center lugs (lugs) are worn down to the same height as the side lugs.

To remove your tire, deflate the inner tube until no more air comes out.

Once deflated, use a tire lever to remove the tire from the rim.

Please check the arrow on the side of the tire points in the forward direction.
To put the tire back on, insert one of the beads (the stiff edge that gives structure to your tire) into the rim.
Once you have done this, inflate your inner tube by approximately 30% before fitting it to the rim (inflating it beforehand reduces the risk of pinching the inner tube).

Next, fit the second bead into the rim, starting at the opposite side to the valve.

Inflate your tire carefully.
The recommended pressure is indicated on the side of your tire as well as on its product sheet (available online).
Also, before each ride, make sure that your tires are at the correct pressure for your ride.

When inflating your tire, make sure you inflate it to the suitable pressure for the terrain you will be riding on and the weather conditions you will be riding in.
When riding in rainy weather, lower the tire pressure to increase the tire's grip.
On the other hand, you can increase the pressure when riding in dry weather.