Transmission Slipping, Checking transmission Fluid, Best preventive maintenance to have done

Do you know where the transmission dipstick is located? Well, just in case, as you stand in front of the vehicle, look to the left and back, close to the firewall, you will see a hexagonal plastic cap (yellow, red, black). With vehicle in park, engine idling, measure the fluid level, if low then add transmission fluid through the dipstick tube. Be sure to add it slowly as it will fill up quickly and is difficult to remove excess fluid if you overfill.

Your transmission fill tube probably has a cap that says for Dealer Use Only instead of a dipstick (my 2011 Liberty does). To check the fluid level, you will need a service tool (a very long dipstick with markings in mm), a fluid level/temperature reference chart, and a means of checking the ATF temp (scan tool or IR thermometer).

Where can I find a service tool/dipstick for it?

Autozone will have it

bars leaks just changed my life. instantly went from no shifting at all, wouldn't go into gear, huge leak on the pavement. Then I put in the bars leaks tranny fix, and immediately it went into gear, then I put another quart of fluid. Smooth driving within minutes, i'm literally blown away right now

You need a new Automatic Transmission Kickdown Solenoid.