Arduino motor shield
Judging by the fact that you agree it looks like this, a search reveals it is a knock-off of the Adafruit V1 motor shield.

Their page shows how to connect to it, and has example code and a library.

I don't really want to post a link-only answer, but the alternative would be to parrot the Adafruit page, which isn't really fair to them because this board wasn't even purchased from them.