Thanks for posting a picture!
It looks like that system was designed to use a single pump. There is room on the pad for a second pump and a heater, but the pipes are not laid out the way they would be for a two pump setup. Also, there doesn't appear to be any sign of a blower pipe.
I can see two ways of setting things up, each of which involves significant compromises.
First, you could stay with a one pump system. To get that to work you would need to add a heater and a three way valve on the pipe labeled pool jets. The three way valve would switch the flow to either go to the pool or to the spa. You would also need to re-plumb the suction side, so that there was a three way valve that allowed you to switch between the spa drain and the two pool suction lines (skimmer and drain). This approach is comparatively simple, but you are not going to get a whole lot of action from the spa jets.
Second, you could install a large dedicated spa pump. This would require adding a very large second pump and a heater, re-plumbing the spa drain over to the second pump, and adding some way to mix water from the pool and spa. This route involves more complex plumbing, is more expensive to operate, makes it much more difficult to use the heater to heat the pool, and the spa jets still won't get the flow they really want.