Not a git repository although git init was typed

My friend is working on a Pokemon Emerald ROM Hack, and he wanted to merge into the Dynamic Overworld System as part of it, like type
git remote add ExpoSeed https://github.com/ExpoSeed/pokeemerald.git in his bash.
However, git remote was unsuccessful despite him doing a few things.

Here is what he did:

• He typed git init before remoting
• He put in the repository URL;
  https://github.com/ExpoSeed/pokeemerald.git in his remote command as seen above.
• He cloned into the pret’s pokeemerald GitHub: https://github.com/pret/pokeemerald and the rh’s pokeemerald expansion Github: https://github.com/rh-hideout/pokeemerald-expansion (because the people at the Pokecommunity Discord Server suggested me to tell him to do so)
• He went into his pokeemerald folder to enter his command
  MINGW46 ~/Desktop/decomps/pokeemerald $ git remote add ExpoSeed https://github.com/ExpoSeed/pokeemerald.git

But despite doing all these, he still got:

fatal: not a git repository (or any parent up to mount point /cygdrive) Stopping at filesystem boundary (GIT_DISCOVERY_ACROSS_FILESYSTEM not set).
If there is a problem with his computer, how could he fix it?