I agree with Matt. Make sure that you bought RAM with matching clock speeds (this will most often be measured in MHz).
Your specific machine should be running PC-8500 DDR3 @ 1066 MHz.
If you need to send those back.... Here is a trusted source. http://eshop.macsales.com/MyOWC/Upgrades...
There you can select your machine to specify which specific processor you're running as the spec in the question were vague.
However... if the RAM is DDR3 @ 1066 MHz...
Try running a PRAM Reset with the new RAM inserted. Hold down opt + command + P + R all at the same time at boot (before the screen appears)... Keep holding through the chime. Your screen will blacken and you should hear your drive initiate... then you can release all keys at the same time once you hear the second chime.
IF ...and only if that doesn't work: Run an SMC Reset. Now, I don't mean to scare you... but I do mean to caution you. Make sure that your drive is backed up on a drive other than the one installed in your machine. It doesn't happen often... but there are certain issues that trigger the SMC reset to wipe your drive.
However, once your drive is backed up and you have tried all the other steps to no avail ... and the RAM is compatible.... follow the directions found here: https://support.apple.com/en-us/HT201295
Good luck, and I wish you the best in getting your Mac back up and running with your new RAM.
This SHOULD work if the RAM is compatible.