#Ensure to have added the directory, if not:
git add FolderName
#Steps to remove directory
git rm --cached FolderName -r
git commit -m "Removed folder from repository"
git push origin master
#Steps to ignore that folder in next commits
#To ignore that folder from next commits make one file in root named .gitignore
#and put that folders name into it. You can put as many as you want
#.gitignore file will be look like this:
/FolderName