Almalexia wants me to take a Dwemar Coherer to restart teh karstangz-Beharn in Bamz-Amschend to make ash storms in Mournhold. I cant figure out what to do.
I am in Bamz-Amschend and can't do it. Can someone out there help me?

Aha! A newbie treading the perilous path of overlooking the 'search' facility. The question has been asked and answered often before. You get a quicker response using search than waiting for Godot to get an answer from the members.

But I have just returned from hols in a giving mood.

You need to get yourself into the right part of Bamz-Amschend. Keep exploring making use of the dwemer explosives on a hole in walls (they are there for a reason) until you come to a circular room with a central 'island' surrounded by water. Walk to the 'island' and search for a moment or two and all will become clear. You must only use the powered dwemer coherer she gives you.

PS there are two places where you can use the satchels. IIRC the one taking you to Radec's Forge is in the wrong direction. You will need that branch later.