First see if it's disconnected. Can you take off the aircleaner assembly (not the filter element, the whole thing)?
The caple has like an orange rubber corrugated covering that keeps out water and dirt. There is a rounded socket on the end of the cable, it snaps onto a steel ball that's on the throttle pivot.
It should fit onto the ball without tension, that's how you know if the basic adjustment is correct. Minor adjustments are OK to make. If it's connected, you can try tightening up slightly by backing off the adjuster a turn or two using a 13mm open end wrench.
If it isn't connected (I've seen this a couple of times) snap the socket back on to the ball, you may be able to do this by hand.