Usually any folder with code inside can be pushed to github or other Online Repository management services!
Go inside your mendix apps root folder, do the below
- Install GIT tools as per the documentation here : https://git-scm.com/
- open the folder in terminal or any other command prompt
- type git init (will initialize the git repo)
- type git add .
- type git commit -m “good description about your code”
- type git push --set-upstream origin <current branch name>