How do you repair items in this game? I mean with a character.

You can only repair things yourself if you're a paladin and have points in the skill mind you.

I know. My character is a paladin, I have a small smithing skill, but I still do not know how to repair items. I do not yet own the game, but I saw it at someone else and played it for a while. Still, I could not find a way to repair a sword. Can you tell me how?

active skills should be put into quick use shelf and be used from there.

Yup, just put it on a quickslot, activate said slot (0-9), and right click. It will bring up your inventory with a hammer/anvil icon that you can click on a item with.

I have journeyman level smithing but i don't know how to repair my gear.

As lothar69 said: Put the skill in a quickslot, activate the slot (the skill should be highlighted then) and right-click. A hammer-anvil-icon appears and you can use it to repair things in your inventory (you need some stamina though).