Ok... Do this way: link your bass to a tuner, and tune it.
Turn the truss rod 1/8 turn in any direction. Wait 5 minutes, then check the tuning again.
If the tuning goes sharp (up), it means the neck it is straighter, so you gnow the direction. If it goes flat, then you bowed the neck.
Usualy, turn right (CW) to straighten, and left (CCW) to losen the neck. But some older basses were built the oposite way.
Good luck, buddy!