When you'll get him:
You get Albel somewhere at disc 1, right after you've secured the Sacred Orb in the Shrine of Kaddan. You have to go to Mosel first to meet up with the King of Airyglyph, then you may go to Airyglyph to fetch Albel. He'll join your party then. Wether this is permanent or not, depends on your actions.

Keeping Albel in your party:
If you'd like to keep him, it's a good idea to visit Peterny right after he joined your party. Stay in the inn for one night to activate a so-called PA. Albel will wake Fayt up in the middle of the night, and he'll ask Fayt whether he hates him or not. You may choose between "yes" and "not really". When you answer with "not really", Albel will stay. If you reply with "yes", or if you don't let this PA happen, Albel will leave. Either Nel or Roger will take his place. He will leave for a short period at the end of disc 1 (Roger and Nel will also leave here, so don't panick like I did on this part). But when you get back to the Kirlsa Training Facility, he'll rejoin your party very quickly if you replied with "not really" on this PA.

But I screwed up!
You haven't done that PA? So you haven't been able to get him? You still have the opportunity to get him. When you've been to 4D-space, you can get him anytime you're back on Ellicoor II. Go to Kirlsa and talk to Woltar, then head over to Crosell's lair in the Urssa Lava Caves. Fayt will have to fight Albel one-on-one. When you win, you can let him join your party. However, you'll have to refuse Pepitta on Moonbase. If you allready have her, then any chance you would have to get Albel is gone. Same goes if you got any of the other optional characters.