If you already generated Les Houches event files, and you want to hadronize them, instead of producing large intermediary files by running Pythia8 standalone, you can now run Pythia8 inside Delphes. If you did not generate hard scattering events, you can generate them directly via Pythia8 inside Delphes.

First, you'll need a working ​Pythia8 installation. The environment variable PYTHIA8 has to be defined.

Generate events with Pythia8 within Delphes

Either way, you have to prepare a Pythia8 configuration file (usually defined with the *.cmnd extension).