Actually, those pots will have one lead at +5V, the opposite at GND, and the middle (called the "wiper") connected to the port. This allows the analog input to run from 0-5V. Commodore used a 500K pot in their controllers, IIRC.
So, for a fully wired port:
1 -> UP Switch (other lead to GND)
2 -> DOWN Switch (other lead to GND)
3 -> LEFT Switch (other lead to GND)
4 -> RIGHT Switch (other lead to GND)
5 -> X-axis pot center lead (other leads to +5 & GND)
6 -> FIRE Switch (other lead to GND)
7 -> +5VDC (to pots, 100mA max.)
8 -> GND
9 -> Y-axis pot center lead (other leads to +5 & GND)
Note: X-axis is the left-right, and Y-axis is up/down. Also, depending on the orientation of the pots, you may have to reverse the +5 and Gnd leads to get the proper behavior.
Pin numbers are typically molded on the back of most DBx connectors, but are really hard to see. Double-check with an LED or VOM before wiring up the +5.
Good Luck...
banzai