Get out your multimeter and start checking voltages into your fuse box. My way of testing if alt is working is to crank the car then disconnect the battery. If the car shuts off, your altenator and/or the connections from it are shot. Then troubleshoot from there. And, I'm sure you've already done this but check your fuses.
You can also check the wires from the installation and see if something is grounding out. That could cause all kinds of problems too.
You can also check the wires from the installation and see if something is grounding out. That could cause all kinds of problems too.