Signal processing using panda board
To connect one microphone to the Panda board, use its audio input. The homepage says it's a stereo input, so yo can actually connect two microphones assuming your microphones are mono. To apply any DSP on the analog signal it must first be converted to a digital signal, of course. For that you need an analog-to-digital converter (ADC). It's an electronic device. You cannot do analog-to-digital conversion by yourself. I suspect the Panda board audio input to have a dual-channel ADC, otherwise it would be quite useless.

I haven't dived into the technical specs of the Panda board but I'd be very surprised if its general input pins were made for analog signals. So you cannot use those for recording audio, because they're lacking ADCs (unless you manage to use the ADCs of the RF interfaces present on the OMAP platform). For each microphone you need an ADC and an interface to the Panda board. Any selfmade solution will be a real hassle here, I would not recommend it.

A possible alternative solution is to use a professional audio interface that has multiple microphone inputs and a USB output. Then connect this audio interface to the Panda board via USB. The challenge here is to get a driver running on the Panda board. But I think it should be feasible. Keep Linux support in mind when choosing an audio interface.

If you've managed that, and you arrange your microphones in a reasonable way you have a microphone array.