I am new. I am trying to create a data base.
You are new. Please, learn also how to use this site so that potential contributors can identify your question is in their field of competence. Press the retag link under your question to replace common (meaning you have a problem with all LO components) with base (the database component).
You can find documentation (“Base Handbook”) in several forms (on-line, downloadable, paper copy) here :
https://documentation.libreoffice.org/en/english-documentation/
Also, since you are starting out, it probably won’t matter whether the version of the document corresponds with your version of LibreOffice. What you probably need at this stage is to understand the general principles of how the data base software works, and to see how to do the most common and simple operations.
You might also benefit from getting the “Getting Started Guide” about LibreOffice in general, to see how Base interacts with the other components of LibreOffice and to understand the operating philosophy of LibreOffice.