There should be clearly labeled + and - marks on the amp. The box should have a + and - connector. Connect those to the amp, and do the same for the inside.
To install the sub, buy screws. screw it in. If possible drill pilot holes.
Also peal and stick the gaskest to the back of the sub to prevent airleaks.
Also, that amp is not very good for subs. Far too weak. That will give it 50W RMS. It likes 300W RMS.
<span style='color:gray'><span style='font-family:Courier'>1995 e36 3 Series RIP
1999 e46 3 Series BURN IN HELL
2000 MR-S Roadster= Current</span></span>