I'd start reading as much as you can. As ambulance corps, you are simple moving the men to the aid station for removal by ambulance. What I can tell you is you should be strong. This is not a job for anyone without upper body strength. At High Tide it was taking 4 men to pull a wounded soldier off the field given some of the geographic features they had to traverse and even then the litter bearers were stumbling and falling. This is very hard work.
Bandaging and administration of medicine was a job for the assistant surgeon accompanying the Ambulance Corps. This is not something the litter bearer would be doing.
Chisolm's 3rd Edition has some information which I will try to type up later for you.
I will also try to include some information on the Federal ambulance corps. As ambulance corps, you are an infantryman in your case detailed to the ambulance corps for the campaign. Dress like a Plain Everyday Common infantryman.
Medical Director Bee's Brigade - 150th First Manassas
Medical Director Evans' Brigade - 150th Leesburg
Medical Director Valley District - 150th McDowell
Chief Surgeon of Division - 150th Seven Pines/Seven Days
Chief Surgeon of Division - 150th Sharpsburg
Chief Surgeon Heth's Division - 150th Gettysburg