Machine hints are directly available after you have started a machine. Please note that a machine must be running to access its hints, and you are only able to access three hints in a 24 hour period. This means that if you access a hint at 8AM, and then a second at 10AM, and a third at Noon, you will be able to access one more hint at 8AM the next day, another hint at 10AM, and a sixth hint at Noon.
Note: Using hints decreases the total point value of the machine. However, hints can also be used for free when you are able to submit all flags for the machine.
When hints become available, you will see the Hints menu option no longer greyed out. Click on Hints to see the available hints, as well as the points associated with each hint.