Why can't I batch rename files?

I have used Lightroom off and on for 20 years. I have had to switch from Mac to Windows PC (very much against my will). Well, over here I can't figure out how to rename files. Can't find it anywhere. I want to be able to import photos and have them named something unique like "picnic" and auto-naming them picnic1, picnic2, etc. I am getting conflicting info; nothing is working. I can do this on a Mac in my sleep, but Windows just makes no sense to me. What do I have to do in LIGHTROOM -- not CC -- to import files after assigning unique names to a batch? Please dumb it down as much as possible. Thanks so much.