It sounds like you are shorting one of the lines out. First thing to remember is to check the legality of monitering phone calls, you are often required to let the partied knwo the calls will be monitered or recorded. As far as the connecetion to the out side box I assume you mean your NID, where the phone lines come in. The easiest way to do this is to use 2 wires for each jack. Basically you would take the first two wires and connect them to the first jack and the seocnd two wires would be connected to the second jack. This way you have two seperate jacks, one for each phone line.

I Swear I did not touch anything bash