Connect a woofer to an output of the crossover. Play some music at a modest level,
If the woofer is connected to the correct output you will hear only bass. If its connected to the mid output you will hear some output but not as much as if it was connected to the bass output. If you here almost nothing then it's connected to the tweeter output. You are using the woofer because it won't be damaged if it's connected to the wrong output. The mid and tweeter could be damaged if you have them connected to the wrong output and played them too loud.