Flying for the first time and as I am a farm girl that's never been more than 50 miles from home I have absolutely no idea what I am doing. My flights are Minneapolis to San Francisco to Melbourne Australia both United Airlines and my main question is:

Do I need to do anything with my checked bag in San Fran between the first and second flights or does the airline/airport handle it for me? I'm getting mixed answers from people (and google is worthless)

Secondly, I don't have a phone with a sim card or data plan or whatever, I rely on Wifi for communication. I'm guessing airports have free wifi, but do airplanes? And how hard is it to find a place to charge your devices in airports or even in air?

(Thanks for taking time to answer my dumb questions. Any general advice is welcome too!)