Don't be afraid to ask questions. Onboarding for new users has improved a bunch in many clients but it's not always easy to understand everything :) A lot of people use the #askNostr hashtag when asking questions, might make it easier to get answers!

For content/accounts to follow, I recommend just going into people's follow lists and hit the "Follow all" button, if your client has it. Or find a client that has it, do that, then switch back to the client you like better in general. That's the beauty of Nostr, the ability to switch apps and clients (almost) seamlessly. (Stuff may break sometimes, but it's generally fine).