Your characters will automatically attempt to identify something when you first acquire it. (The best Artifacts skill in the party determines success, but every character has a chance to improve their skill.)
If they are unable to do so then it will remain unidentified with a big question mark over the icon. There are two ways to identify it at that point:
Use an Identify spell, which is occasionally found on scrolls, but can also be learned by characters with Divinity or Psionics - you'll be able to buy books of that spell in Arnika, among other places, if you don't take it at level-up. You need a minimum skill level and it can use a lot of magic points (Mental), so this option can be difficult (or at least time consuming) until the caster has trained those skills up a bit.
Wait until your characters' Artifacts skill has improved. If you right click an unidentified item to examine it, it will re-test your Artifacts skill to see whether the item can now be identified. (You won't get any skill-ups this way - that only happens when an item is first acquired.)
Post edited June 04, 2013 by Garran