Ah…. what I perceive is a simple question isn’t so simple if a person hasn’t ever done it, is it?
Here’s what you need to do.
First off, don’t worry about the fact that your compressor can generate 300 PSI. That’s a good thing.
On the discharge line from the tank to the coupler where you would connect an air line is a regulator. Not sure what this or does? Here’s complete info on air regulators.
All you have to do is “dial down” the pressure reading on this regulator (watch the gauge) to whatever pressure level you want your downstream application to see.
In your case, if you want to inflate tires without bothering to check the resulting tire pressure, set the regulator to the recommended pressure of your tire. That’s usually in the area of 35 PSI for light truck and car tires, but you need to look on your tire or on your car’s door post for the specs for your vehicle.
You connect your air line to the compressor discharge coupler. Here’s info on those.
At the other end of the air line you need to have a tire filler tool (tire chuck) installed. The photo above is one of those.
One end fits onto the valve in your tire to allow air to flow in, and the other, with a connector installed, connects to the coupler on the end of your air hose.
Once you’ve got it all installed and connected, push the tire chuck onto the fill valve of your tire and the air will flow from your compressor into the tire and fill it to the pressure on your regulator gauge setting.
Make sure you set the regulator to the right pressure, or add air to the tire and then use a tire pressure gauge to check the tire. Make sure you don’t overfill the tires.