A 2 channel amp is right and left channel. If you want to run separate channels to highs and mids you need 2 amps (4 channels).
To run both highs and mids from the same channel you need a crossover that splits the frequencies to the correct speakers. What speakers are you gonna use?
I just bought a 2 channel rockford fosgate amp. and 2 10" subwooper speaker. My question is how can I do wiring connections with my stock stereo in my honda civic without buying anymore stuff. All I have is the wiring kit and a converter for RCA jack because my stock stereo does not have RCA jack to connect in my amp. and I dont which side of my stereo speaker output to go to my amp input.