Okay, since nobody else has taken a crack at this one I'll give it a try. The way this works on my '66 is as follows, and should be very similar to what you see on your 68. Looking from the drivers side fender down towards the bellhousing, you should be able to see the shift fork which holds the throwout bearing poking out of the bellhousing. Just in front of this is a threaded rod that goes into a six sided, pointed adjusting "nut". The pointed end of this "nut", for lack of a better term, fits into a pocket on the clutch fork. This assembly is the clutch adjustment for setting the position of the throwout bearing with respect to the pressure plate. The position of the adjusting nut on this threaded shaft is locked in place with a jamnut that runs up to the back of the adjusting nut. To adjust the distance between the throwout bearing and the pressure plate, loosen the jamnut and then turn the pointed adjusting nut on the shaft. Both the jamnut and the adjusting nut need a 9/16 wrench. To increase the distance between the throwout bearing and the clutch fingers, run the adjusting nut up the threaded rod. This will make the engagement/disengagement point of the cluch closer to the floor at the pedal. To move this point further up the travel of the clutch pedal, you'll need to move the throwout bearing closer to the the pressure plate.
If by "releases" in your post you mean engages, then you need to move the throwout bearing away from the pressure plate. I normally adjust my clutch one full turn of the adjusting nut at a time. You can only get about one 1/6th of this adjustment at a time with an end wrench. Once you made the adjustment, tighten up the locknut against the back of the adjusting nut to make sure everything stays where you put it. If you've never adjusted a clutch before, now is a good time to get underneath the car with a flashlight and look inside the bellhousing alongside the clutch fork. You should be able to see space between the throwout bearing on the end of the clutch fork and the fingers of the pressure plate. If the bearing is against the fingers with the motor off, it will be constantly spinning during normal driving and will wear out very quickly. Changing this bearing means pulling the transmission, so make sure that there is some space between the two with the motor off. Incidentally, this distance between the bearing and the pressure plate is called the "freeplay" in the clutch linkage. You also need to make sure that there is freeplay in the system when the motor is at RPM as well. The easiest way to do this is to put the tranny in neutral and take the motor to 2500-3000 RPM. Put your foot on the clutch and slowly depress it. You should be able to distinctly feel when the surface of the throwout bearing comes into contact with the pressure plate fingers as a chatter like vibration in your left foot. If you feel this point right at the top of the clutch pedal travel, then the throwout bearing is too close to the pressure plate. Stop the motor, let the exhaust cool off, and readjust the clutch accordingly. Once you've got positive freeplay at idle and at RPM, take the car for a drive and see where the clutch engages and disengages. Adjust the bearing position until you've got the release point to suit you. Hope that helps, feel free to message me if you have any questions.