Should be hex screws, 2 each, on the saddles for the strings. Turn 'em to the left and that should lower the action. Don't go too low or you'll start buzzing on the frets.

It should look something like that. The hex screws are in red. turn them to the left to lower it, and the right to raise it.
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Two ways, if the neck has too much bow then straighten it by tightening the truss rod 1/4 turn each time.
If the neck is OK then lower the bridge saddles.
Remember that if you lower the action you will flatten the the note at the 12th fret, you will then need to move the bridge saddle forward slightly.
Before carrying out truss rod adjustments release the string tension.
When adjusting the bridge saddle release tension on that particular string.
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If you have a $1000+ bass and do not know how to adjust action, intonation and neck relief yourself, take it to a guitar tech and have them do it while you watch and learn.
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