Welcome aboard!
Others will give you far better advice than I, but here is my tuppence worth:
Start slowly play slowly. I started a couple of years ago, in my '50s, and it takes time to get your fingers to move and most people don't normally stretch their hands much. You will be able to cover 3-6, maybe even 1-4 over time, but don't stress now. Start further up the fretboard where the frets are closer together and life might be easier.
I found studybass.com really useful when I started, other sites re available and there are online tutors here too.
Oh yeah, one other thing, which a good friend of mine said. If it was dead easy, everyone would do it and it wouldn't be cool, right? 😎