Camping is not a part of the class skill set.
This skill is used to cook food in a fireplace or to complete a wanderer’s skill set.
Using BedRoll near a fireplace allows your character to log out quickly.
Your main class skill won’t decrease if you train Remove trap.

Skill efficiency

You must have sticks to use the skill. Use them on the ground to make a fireplace. You can cook food standing close to the fireplace.

For a fast log out of the character, there is an option of using a BedRoll near the fire.

Ways of leveling your skill

Use Dagger on a tree to cut sticks.
The sticks can be used only on the ground.
If you have no house or a boat, place the sticks down in small quantities.
Keep in mind, that all the times disappear from the ground after some time, except when they are placed in boats or houses.

Here is a detailed video of how the skill is used: