There is a lot of different tackle involved in fly fishing.
The basic equipment includes
fly rod. 9ft is a good length, floating fly line and a suitable reel
Then you need a leader, probably ending in about 8lb. To that you would tie a tippit which could be fluro or mono. This area is quite complicated but I suggest buying same 4X mono to start with, it should have a breaking strain of around 5.8lb.
Then you would need a selection of flies….
What rod do you own?