For reference, such a mic is typically called a condenser mic rather than a capacitor mic. Condensor is a former term for capacitors, but condenser continues to be used to describe microphones that work on the principal. That's a type of mic that uses changes in an electrical field between two wires to detect sound and it is more sensitive in general than a dynamic mic which is basically a speaker in reverse.
Low cut is used to roll off the lower frequencies when you are micing something that doesn't have lower frequencies, but you do, so you want the lo cut set to 0dB.
+20dB Gain is a boost from a pre-amp. You shouldn't use this unless you have to because it is otherwise likely to make your signal too loud.
P-Pwr +48v is phantom power. It is a way of providing power to a microphone over the XLR cable if it is needed. In the case of a condenser mic, power is required, so this should be on. If you microphone had a battery built in, it should be able to be removed.
Phase Reverse flips the waveform. It is only useful for mixing different signals and you are not doing that, so leave it off, though the setting really doesn't matter.
I'm not sure on the OPL, but I'd leave it off.
The input dial will adjust how much amplification is applied. You want to apply enough amplification to get good signal level, but not so much that it clips (exceeds the max volume of the pre-amp).
The VU meter is a measure of how much signal power you are getting. Watch it to see if you are clipping. The needle should never go all the way to the right. If it does, turn down the input gain.
Note that you can only get mono audio with this setup as you only have one pre-amp and thus only one channel recording at a time, but that shouldn't really matter as long as you get decent quality audio recorded and then assign it to both the left and right speaker.