How am I supposed to connect this potentiometer to the PCB?
I see five holes for connections to the pot.
There is one hole in the center of the pot drawing on the PCB - that hole is for the wiper of the pot, and should be connected to the center terminal of the pot.
The board has two holes for each end of the pot - probably the board designer had two different parts in mind when he laid out the board, and made provision to use either one. The two outer terminals on your pot connect to the two outer holes in the board.
The pot you have is meant to be mounted to a panel using the bushing around the shaft.
There are two possible holes on the PCB for each pin as you can see in the picture, use any or both if you like. Also pin 1 and 3 can be swapped but 2 from PCB need to be connected to 2 on the potentiometer.