rough gist to get you going (somebody else can fill in the details).
You have to score 2 or 3 (I think) good results in tournaments.
'Good results' = equal the score that is considered the norm that a GM would score in the tournament. Therefore the actual score you have to get varies according to how strong your opposition in the tournament is.
I think you have to have a rating above 2500 too.
Also I think maybe one of your results has to be in an all-play-all tournament.
a) get 3 GM norms (3 performances in tournaments with a TPR (tournament performance rating) over 2600 - against quality players)
and
b) at some point in your career have a rating over 2500 (this doesn't have to be a rating over 2500 when FIDE publishes its ranking list, just a rating calculated to be over 2500 after some individual game)
Or....
You can get your countries chess federation to organise 3 tournaments
filling them up with 3 of your countries chess players and the rest with
GM's from a few Eastern European countries, let us say just for the
sake of an argument. Bulgaria & Romania.
Lo and Behold. Your three players get GM norms in the first tournament.
Amaziing. Your three players get their 2nd GM norms. in the 2nd tournament.
Wow!....etc etc.
If you are one of the lucky three you get a GM title for playing legal moves.
Now I wonder if that has ever happened? 😉