Setting ground targets for enemy ground pounders

[SierraFox]

I've been messing around with the mission editor to get a feeling for it. I'm wanting to make a mission where it's your task to stop an enemy plane and artillery from attacking an airfield. however i want the airfield being attacked by the time you arrive. I'm unable to find a way to mark an attack target on an airstrip for AI or does there have to be some kind of ground unit that they are attacking?

[dooom]

you need to read up on the advanced waypoint - it will open a new frame to allow you to select targets etc - read page 144/152 of DCS user manual. That should point you in right direction.