Place the desired ESR version (dvdv direct mostly) as ESR.ELF in your BOOT folder and set up the ESR path in your config with the FMCB configurator. Wenn you now launch a ESR "Video-DVD" within the hacked OSD it should boot up ESR automatically.
As second option, you can launch your esr .ELF file or the ESR GUI with uLaunchELF while a ESR disc is in you drive.
Slim PS2 SCPH-70004 (v13) w/ FMCB, 3x Sony 8MB, 1x MaxMemory 16MB (Backup card)
I'm not available for FMCB installation service until I can guarantee a processing time of a few days again, sorry.