Like most other music instruments (unless you're my wife, who can pick anything up and play it well... so envious of her ability to do that!), I simply got a teacher and have been having weekly lessons. A decent chunk of my "homework" ends up coming from this book if it isn't his own homework:
https://www.amazon.com/gp/product/1540024091/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Building up all the independence has been the most difficult part so far, but, I'm certainly appreciating the instrument a TON more than I have, and, in the end, I feel like it'll allow me to be a better bassist, as well.