How obtains the graph ER of the DB ???

[Sebast0p0L]

Hello, regards from Colombia, I am editing OrangeHRM for a work of degree in my university.

I have a problem, need the graph Entity Relation (ER) of the database, to be able to create a script that fills the DB with information of test.

Someone of you, does it know where I can find the graph?, might they me send it?
Or in counter case, they might indicate me, how with the sources I can make inverse engineering and obtain it?

Thank you for a prompt response !!