Samsung Android

I just purchased this unit. Last Kindle just stopped working won't turn on won't charge. So I purchased Samsung. So far so good. Bit of a learning curve. My question concerns Calibre Companion. Loaded it with no problem. Took a bit to figure out the download process from Win 11 PC, but after that it works beautifully. I have about 30 books loaded onto the pad. How do I create new groups by subject Fiction, Non fiction etc. And then move books accordingly
Thanks
J Welk