Welcome to the forum!
Just purchased then do the basics:
Start with the basics: tune up for sure. Plugs, wires, cap,rotor, and the fuel filter. Clean the throttlebody.
You are throttlebody injection so the computer controls idle. There are several adjustments that are essential for the TBI when you replace a sensor. If you don't have a multimeter get one. You need it to setup and troubleshoot. At idle the coolant temp sensor (The YJ has 2, the one in the rear is strickly for the temp guage the other one on the manifold is the one for the computer) is the primary sensor for cold idle and sets up the calibration unil it goes into closed loop after it warms up and uses the other sensors.
Download the service manuals in this thread: