How do you connect a right and left out jack on my head unit to my amplifier that has 2 input jacks for front and 2 input jacks for back?

To connect your head unit's right and left output jacks to your amplifier, use RCA cables. Connect the left output from the head unit to the left input of the amplifier (typically labeled as "Front" or "Back" depending on where you want to send the signal). Do the same for the right output. If your amplifier has separate front and back inputs, you can choose to connect to either set based on your desired configuration, but ensure that the left and right outputs from the head unit match the inputs on the amplifier.