I think this is the video I first used to help me get setup

Also read the Getting Started Section on the HA website.

From there, you can look into which Home Assistant Integrations you might want to use, and start to plot how you'll get up and running.

Some notes:

• it is very flexible, which also means it takes some effort to get things working
• some of the integrations still send out to the internet, so keep an eye on that