The "-" button raises control rods, this heats the reactor. The "+" button lowers control rods, this cools the reactor. The coolant slider below those buttons' cycles through coolant pump speed. You can see the speed in the top left corner. You can also see how much the control rods are inserted in the reactor. The top left shows the turbine RPM, the higher temp = higher RPM. The left shows your, "Shift Points". Sync your turbines at about 2000 RPM to generate Shist Points. The main goal is to get the required amount of shift points.
Your main goal is to get enough shift points for your pay, don't let it get too hot... New features - Reactor design change I gave the reactor a new look, so it looks better because it's supposed to seem like it's from the side