If they are under 60, get it from the airport immigration building. You will need your passport, your RP, a copy of their passport, a filled up form (its pretty simple to fill) and your ATM or credit card.
If they are over 60, I think it may be more difficult to get and you will have to go to the main immigration department building (which is close to the Al Gharrrafa interchange). Ask around there and you will be guided. Essentially you will be required to meet an official on the first floor of one of the buildings (he is the guy who deals with "exceptions".)
If they are under 60, get it from the airport immigration building. You will need your passport, your RP, a copy of their passport, a filled up form (its pretty simple to fill) and your ATM or credit card.
If they are over 60, I think it may be more difficult to get and you will have to go to the main immigration department building (which is close to the Al Gharrrafa interchange). Ask around there and you will be guided. Essentially you will be required to meet an official on the first floor of one of the buildings (he is the guy who deals with "exceptions".)