how to setup an off line installation is described in the wiki.https://www.guildofwriters.org/wiki/Playing_Fan_Ages
If you have the zipfile from a fan age then first unzip it , it will contain several directorys
Every directory will have a few files inside.
the directorys are named
dat, SDL, Python and sfx
inside your installation you will see directory's with the same name.
you need to combine them.
in other words everything inside the "dat" folder goes into dat
everything inside SDL goes into SDL and so on.
That is all what you have to do.