Putting Together Your Setup
Now that you have the necessary tools at hand and you've experimented with some playing, it's time to set up your bass rig. First, you should attach the strap to the bass. You may have to adjust the length of the strap so that it doesn't hang too low or high. Make sure that the holes on the strap are secured fully over the strap buttons at both ends of the bass guitar body.
Once your bass is in tune, connect the cables and plugs. Then find an AC outlet so that you can plug the amplifier in. Once you're plugged in, if your amp has a standby switch, engage it so that it has a softer startup. Also, turn the volume controls all the way down. Be careful: there may be multiple volume knobs, or attenuators. Now you are ready to turn the amp on. After switching the amp's power on, give it a few moments to warm up. In the meantime, insert one end of the guitar cable into the jack of the electric bass, then insert the other end into the first jack (sometimes the only jack) on the left side of the amp.
Be sure to always consult the owner's manual before using any electrical device. Overall, tubes are more finicky than transistors. Consequently, tube amps should be turned to standby for at least one minute before use. After use, turn your tube amp to standby again until the tubes cool.
At this point, if the amp has a standby switch, bring it out of standby. Turn the bass guitar's volume knob up slightly — about halfway. Next, slowly turn up the master volume knob on the amplifier. You may or may not hear anything by now. Play a note, any note. If there is no sound yet, you may have to turn up the preamp gain knob or the other volume knob(s) as well as the master volume. If you only have one volume knob and there is no sound, turn up the volume knob on the electric bass and amp until there is sound. Eventually, with some experimentation, you should be able to achieve a basic amplified sound. Now, make some noise!