Jeremy, you have to take off your cowling on the right side below the dash. You remove the two bolts in the center under the steering wheel, then raise the hood and remove two on the firewall. There are three similar bolts on the firewall, but only the bottom two need to be removed. The top one holds the instrument panel cowling in place.
Once you remove the cowling with the ignition switch. You will see the bottom of the throttle lever and pivot point. The nut at the pivot point needs to be tightened. You can use some Loctite type thread sealant or find another nut and lock it in position by double-nutting the bolt. I tightened mine with nothing added over 8 years ago and it is still fine, so tightening may be all you need.