Here's a quick beginner's guide to start. I'll give you everything I've learned listening to 10,000+ hours of audiobooks and podcasts.
If you're just starting out it can get messy and if you're not careful you can wind up with an assortment of misaligned apps. The apps that people usually start with are phone dependent, e.g. android vs apple. Android phones have Google Podcasts and Google Play Books. While iPhones have Apple Podcasts and Apple Books. Before you lock yourself into one side or the other, consider interchangeable apps. For example, Stitcher and Audible. If you start an account with Stitcher or Audible you can download the app on pretty much any smartphone.
In my opinion, I prefer Stitcher and Audible because of their versatility. Also, when it comes to Audible it's easier to share with your family. Know this: if you start using the native apps for Google or Apple they link straight to your personal Gmail or Apple account. This is problematic if you want to share your virtual library amongst your family. What worked best for my family was to create one shared Audible account that we all can log into at the same time. Now the whole family shares one virtual library independent from our individual Gmail and Apple accounts. Note: when it comes to podcasts there is no need to share a library, so everyone is free to start their own individual Stitcher accounts.