I drive a '73 Super Beetle - guessing it's the same as yours.
Anyway, here goes.
You should find three round knobs on your dashboard, two of the same size and one slightly smaller. The smaller one, to the left of the other two, should click into three positions and controls the speed of the blower fan (located in a small box in the trunk with the windshield wiper components). Air for this system comes through the small patch of louvers right in front of the windshield (outside) and can be diverted to the inside of the windshield or the occupants using the two larger knobs. Both knobs work the same way, counterclockwise to open (allow air to pass) and clockwise to shut. The left knob lets air come through to the inside of the windshield, the right one to the occupants (through the small passages above the radio opening). You can use any combination or amount of open/shut of each knob at the same time. You can also use the system without the blower fan on, sort of "ram air" style. I don't recommend you turn the blower fan on with both knobs "shut" - seems like it might be bad for the system.
The levers near the e-brake open flaps in the back to let heat into the car from the exchangers. Pulling up on the righthand lever (like you would the e-brake) opens the flaps and turns the heat "on". The lefthand lever directs the hot air more to the front of the car with the lever "down" and more to the back of the car with the lever "up" - for example, you get the most defrost by moving the righthand lever up and the lefthand lever down. Again, both levers can be used in varying positions independently.
You should realize that the two systems are completely separate - one does not control the other in any way. But, if you choose to drive during the winter, you may want to experiment with the fresh air (dash controlled) system - cracking it open slightly sometimes seems to help pull more heat into the car, or help the defrost circulate across the windshield better!
Good luck, hope this helps.