OK, so this is where it doesn't make sense to me. If he wants the player to shoot three shots from the middle of the table, why not all four? Why would he designate the starting point someplace other than the middle? Maybe he's giving you a break for the first shot.
Let's say that's his intent for whatever reason. You can shoot either number 1 or number two from the designated cb spot. With shot number 1, you will have to spin the cb with low outside (right), using a fairly light stroke (but not too light to where the backspin doesn't take), timing the backspin so that there is only a little left on the cb by the time it reaches the ob. This is a spin shot.
To shoot number 2 from the starting point, you will have to use more force, again with the combination of low and outside (left), but I would say, not as much backspin as with the other shot or the cb will not hit the rail soon enough and wind up drawing back off the rail at a more obtuse angle. You will have to experiment to find the right combination of the two spins along with the desired amount of force.
Shooting any of those shots from the ring in the center of the table will depend on the table conditions. The faster the table plays, the harder it will be to hold the cb. This is a finesse shot --- again, low outside, but with a kill stroke to kill the speed of the cb as it comes back off the rail. That means you will have to time the point at which the backspin wears off more precisely than shot number 1, but with enough side to bring it back towards the middle. I have found that a shorter bridge length helps here. If you over-stroke the shot, you could scratch cross-side. (On extremely fast tables, you may have to allow the cb to run back and forth across, which changes the shot.)
These shots are among my favorite shots to shoot and are a must to know, especially if you play 9 or 10 Ball, where they seem to surface fairly often. However, they are pretty advanced and will take time to learn to master.