Hi there! I've only used the "EP128Emu" emulator which looks to be available for download at: http://www.ep128.hu/Ep_Emulator_eng.htm )
You will need to set the machine config to 128K memory.
You will need to have segment 00 set to exos21.rom
You will need to have segment 04 set to basic21.rom
You will need to have segment 10 set to epfileio.rom
and in Options you will need to set the working directory to the files subfolder.
Hope that helps.