Like a frame…
If you really need basics, look here https://wiki.documentfoundation.org/Documentation/Publications#Getting_Started_with_LibreOffice, e.g. “Getting started with Draw”. Otherwise you need to be more verbose. How looks the shape you want? For what purpose you need it? What do you have already tried?
Since these can be multi-page documents, I realized that I can have a page of “samples” that I can copy from. Simple once I thought about it.