Connect a patch cable to the output patch of your preferred effect. In a typical recording studio, effects units are hardwired to a patch bay. A patch bay makes connecting the various effects to different desk channels much easier and tidier. This prevents the need for you to access the rear of each effects units whenever you want to hook it up. The patch bay jacks are typically numbered, rather than named. If you aren't sure which patch corresponds to which effects unit, consult the studio's patch bay legend. This is a standard document that lists which effects units are connected to which patch bay.
Connect the other end of that patch cable to the input jack of the first vacant auxiliary channel patch.
Connect a second patch cable to the output jack of the auxiliary. Connect the other end of this cable to the input patch of your preferred audio channel. If you want to record reverb onto the guitar track, route the reverb to auxiliary channel one, then route auxiliary channel one to the channel to which the guitar is routed. Typically you route effects to a channel after the audio is recorded. This gives you the option to keep an unaffected take.
Press play on the recording console. This enables you to hear the effects in real-time as the recorded guitar plays back.
Adjust the parameters of the effect to your preferences. If using chorus on a bass, tweak the rate and depth parameters.
Press "Record." By hitting record with the auxiliary channel wired in, the audio is sent to the Aux channel, routed back to the desk and then to the recording device, where it is "printed." There is no way to undo the recording of an effects send recording in an analog studio, so make sure you like what you hear before recording.