You need two Apps on your Samsung, one of which you may already have.
First make sure that your Samsung is connected to your home internet. (Same as your computer)
On the Samsung go the the Google Play Store and download "Calibre Companion Demo Version" - it's free but is limited to 20 books on the tablet.
On the computer open Calibre and click on Connect/Share (in the top row of icons), then on "Start Content Server"
On the Samsung open "Calibre Companion Demo Version" (might just be called CC Demo)
then touch CONNECT in the top right hand corner and then touch "to Content Server"
You should then get "Index of content server" and can select By Title, By Authors, etc
Select a book and then touch DOWNLOAD
Repeat for as many books as you want and then touch DISCONNECT
You can shut down Calibre on the computer now.
So on the Samsung you will see the books that have been transferred
Touch to select one and then touch READ in the top right hand corner
The book should open, but if not you should get a message inviting you to download a reader app.
You need to do that - through the Google Play Store.
Downloaded books should appear in the Samsung Docs or Documents file.