how to take already created repository from github code example

Example: turn a folder into a git repo

$ git filter-branch --prune-empty --subdirectory-filter FOLDER-NAME  BRANCH-NAME 
  # Filter the specified branch in your directory and remove empty commits
  > Rewrite 48dc599c80e20527ed902928085e7861e6b3cbe6 (89/89)
  > Ref 'refs/heads/BRANCH-NAME' was rewritten