I assume that you are using the “standard” JPA toolchain (JPT), as you did not specify otherwise.
First you need to define a connection (in Exlporer data source). You should be able to expand and see the actual tables you need to work with:

"JPA Facet", JPA Facet JPA: " " , "" ":

( , JPA Tools > Generate Entities from Tables...), :

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