If you haven’t played before, use your 4th finger on the fundamental bass row—the one with the indented or rhinestoned C bass button, and play bass-chord 4-3. If you’ve already learned 3-2—as I did back in the dark ages—use those and you’ll be fine. The 4-3 formation has the advantages of encouraging you to drop your wrist and of making alternating bass easier—4-3-2-3 or 4-3-3-2-3-3 etc.
Adjust your bass strap so it’s loose enough to let your wrist slide, but keep it tight enough so your palm doesn’t lose contact with the box as you pull out.
Drop your wrist toward the floor till your 4-3-2 fingers line up with the bass row you’re playing.
Learn to keep your fingers quiet and on or close to the buttons. Most of us can’t do this from the start, but you can learn it as you go along. Then later it’ll be easier to hit bass jumps and to play fast.
Arch your wrist so the last segment of your fingers comes straight down on the buttons. This minimizes hitting multiple basses when you don’t want to.
When it’s convenient, do your bass jumps up while pulling out; down while pulling in. This idea comes from Charles Magnante’s first method book.
As a default, keep basses and chords staccato. But there are many times you’ll want them longer, especially when the left hand is providing harmony. Staccato bass has the advantages of giving you a better metronome, making the bass side less overwhelming to the treble (right hand) side, and enabling you to play fast later.