Adjusting the throttle cables
The adjustment for the throttle cables is visible and accessible on the right side of the right carburetor. You can easily see how it works and adjust it with a suitable wrench (probably one of those in your tool kit.)
Your throttle cable needs a little slack in it to keep from being pulled when the bars are turned. This adjustment has important safety implications. You want your engine to be able to return to idle.
Under normal conditions one can feel the little bit of slack in the cable that must be there, maybe 1/8" when you turn the twistgrip with the engine not running.
There is no need or reason for anybody to disturb these cables under ordinary conditions, except to lube them.
If you look at the adjustments and work the twistgrip you will see what is going on. You see the cable pulling the throttle open. The adjuster increases or decreases the amount of play in the inner cable. The 'return' cable is there only for a safety feature in case of a binding throttle, but does not do anything under normal conditions. But the return cable also has to be in adjustment, so that it does not interfere with the operation of the actual throttle cable that opens the throttle. Check and lube both of them, and they should last a very long time.