Computer Beeping and Won't Start

Hello,
I have just tried installing a second hard drive on my computer. When I finished connecting everything, I turned on the computer but it made a series of beeps and nothing shows up on the monitor. There are 6 beeps in total but im not exactly sure of the order. If i had to guess i would guess 1-3-2 or 1-2-3. What is wrong and how do I fix it?