My question is how can I check the oil pressure.

First some background and history. I have 914 1974 with a 2.0 fuel injected engine. PO said that the car sat for 15 years. When i got it first i changed out the fuel pump, new gas lines redid the gas tank, changed the oil, inspected with a camera through each spark plug. All looked great! Put some mystery oil in each cylinder and turned a little each day for about a week very carefully. Adjusted the valves new plugs and buttoned up. Installed fresh gas and started the car. Ran great blew out some mouse poison and some smoke of course. I did not run it to long because i would like to know if the oil pressure is ok.

I would say if you got that far, you can go the rest of the way. You can add an oil pressure gauge at the place where the idiot light switch is installed. A manual is in your future anyway, and that will show you where the parts are. If the idiot light goes on with ignition before starting, it probably works.

If your car does not have an oil pressure gauge, sounds like it does not, I would buy a matched VDO oil pressure sending unit and gauge and install it. Try North Hollywood Speedo or Palo Alto Speedo if they can't hook you up I am sure they can refer you to someone who can. Pretty basic install. If you do not have a center console that would accept the gauge, you could just add a 1 gauge pod under the dash to accept the gauge.

I can't imagine driving one of our cars without an oil pressure gauge. Good luck.