Technically, how to time the distributor?

[Topless]

Novice mechanic here. I bought a timing light to set my ignition timing and am ready to go but also read that the distributor rotor should point at spark wire 4 at TDC. I've never touched a distributor before but believe the rotor is the red line I see when I take the cap off. How do I position it? Youtube says to loosen the screws but that only loosens the cap, and I am unable to turn the unit. Apologies for the basic questions.

[PaulC]

Loosen the hold down clamp at the base of the shaft on the left side.
A crow foot wrench will make it easier to access.

[bobplyler]

Here's a picture of the distributor. There's a bolt holding a fork like thing that holds the distributor in place, under the main part of the distributor. Not the easiest thing to see or get to.