How 2 catch feebas

You can't get Feebas in Fire Red.
You can,however,Trade one from a Ruby/Sapphire/Emerald GBA game.
Hope this helps!

Feebas isn't available in FR.

Ya. The only way to get a feebas is to treae from one of those games.

Feebas can only be acquired in the Ruby,saphire,and Emerald versions

You cannot catch Feebas in Pokemon FireRed and Pokemon LeafGreen. You will need to Trade from ether Pokemon Ruby or Pokemon Sapphire or even Pokemon Emerald. If you have not beaten the league with over 50 Pokemon seen I think it is, you will have to do that. Then you can unlock the trading for Pokemon Ruby, Pokemon Sapphire and Pokemon Emerald. I hope you found this helpful.

In my hack game from fire red it is Pokemon darkcry the legendaru dogs disguise as:

Uxie-No 243 (Raiku)
Mesprit-No 244 (Entei)
Azelf-no 245 (Suicun)

I see them lower in the Pallet Town where there are tangelas

You can only get feebas in Ruby Sapphire and Emerald and then Trade it over but it is too hard to get in those games so don't try