Here you go, bookmark this site, I use it a lot
Parallel Resistor Calculator R1 + R2 = R equivalent resistance circuit equivalent total resistor finder made easy piggyback = parallel - Eberhard Sengpiel sengpielaudio
www.sengpielaudio.com
You add the resistor to the two outer pins of the pot. There's a couple of different ways to do it. You can solder in the pot and add the resistor to the solder points on the board. Or, the way I do it is just mount it on the bottom side of the post and push the pins of the resistor through the little square holes near the body of the pot.
"Black and gray circular items"? You mean the electrolytic capacitors?