There are loads of manuals out in the wonderweb, but to be more precise, you need to know your fridge model number. Mine is on a label inside the fridge, generally starts with RMxxxxx.
Electrolux became Dometic several years ago so don't be phased by the change of name, the fridge is the same.
This link http://www.club80-90.co.uk/pages/downloa...troluxRM212.pdf is fairly typical for an older Electrolux fridge. It may be sufficient for you to get yours working.
Getting a fridge to fire up on gas can be difficult if it hasn't been used that way for a while. You quite often get a blockage in the burner gas jet, usually a spider's web which will have to be cleared.
Anyway, start off by finding your exact model for complete instructions :)