Easy BPY is a module created by Curtis Holt to simplify the python API. You can find more information in the documentation:
To use it with Serpens you can simply install it as explained in the documentation and start using it in your scripts. For this, you can use the run script node. You can see if Easy BPY is installed in the node editor N-Panel under Settings.
ā¯—Different from how it was with Serpens 2, you now need to import easybpy in your script as explained in the module's documentation.