Hi. What exactly do you need to know? I've been a huge fan and user of Publisher for over 20 years and still think its the simplest page layout program that produces pro results there is. Nothing compares.
Even back in the mid 90s people used to thumb their nose up at it, but it always did what I wanted it to do so for me, simple and straightforward and got the job done!
Basically you start with a blank page, then you can add text, picture, word art or table boxes to the blank page. Use borders and assorted tools to make it look prettier or use one of their templates. Its all drop and drag so you can experiment to get the design you want. There are of course multiple page sizes and templates for everything from a booklet to a business card to a birthday card, all manner of menus and leaflets. Full control over the page and the text and diagrams on it.
Back in the day, I even used it to lay out web pages and always used it as word processor. I could get the result I wanted without using complicated programs like Word!
If you need professional print, printers marks can be added for alignment, you can even print using 4 colour separations ready for a litho printer.
So, I recommend it still to this day to anyone. If you need specific help with a project then feel free to reach out and I will share my tips learnt over the years.
Great question and glad people still mention a great and under appreciated piece of software :-)