newbie concerns about automatic sign on

I just started using 1Password last night and am feeling very overwhelmed. Very concerned that 1Password allows me to automatically sign on with the link with my master password and secret key without me manually inputting my master password. it seems that if anyone was on my computer they could access my passwords. I had Dashlane for years but have been wanting to change to a better password manager.

One of the main reasons I wanted to leave dashlane is because they changed to just an online program and I could no longer use a yubikey.
Right now I want to set up 2FA and use the google authenticator on my iphone that I use for dashlane. Can I use that authenticator for 1Password or do i need to put another authenticator on my phone. I am going to order a yubikey because I lost mine but not sure which to get. I am an older women and this may be too difficult a transition. What is the best and easiest way to learn how to use 1password. Prefer video.

1Password Version: 8
Extension Version: 2.8.1
OS Version: windows 11
Browser:_ Firefox