Hi Victoria!
If the wall is "free standing" - not buried under the earth on any side, than you can line it up with the tar paper and wire mash, add white cement to the scratch coat. Do not go all the way to the ground (leave a minimum of 18 inches). You will not
need moisture to be "traveling" from the ground up. Make sure that the roof above the wall has a proper awning and there will be no rain water running down the fresco from the roof or the wall above the fresco.
If any part of the wall is under the earth or if the wall is moist, than you will have to create a "fresco wall" and anchor it to the existing wall about an inch+ away from it. To do so line the existing wall with tar paper, fasten studs over (2x4 will offset the fresco wall 1.5 inch away), put tar paper over again and wire mash to hold your scratch coat. Good mason should be able to advise you in detail on this, just make sure that you explain that you must keep salts and "standing" moisture away from your fresco.

Good luck

Ilia Anossov.