Im new to this forum and want to say hello

Ive build a PXE Boot with Porteus Kiosk 4.8.0 and its working totally fine! Now ive a new requirement... We want to create an autologon to a specified intranet site which needs credentials to authentication. I found this faq: https://porteus-kiosk.org/faq.html#18
I also find several forum entries about saving credentials to firefox, but im not sure which would be the best way. I think the faq article wont work with pxe boot right, because of only read only? This would be my prefed and easierst way.
To modify the image would be also ok, but I dont know how to edit the 4.8.0 image. The tutorials seems to be for the older versions.
Can anyone assist?
thanks in advanced.