In Windows, right click on your repository → click on Open a shell here.
You will see a command prompt.
Type git push in it. (been aware after seeing SimonBoudrias comment)
The command prompt will suggest you to type some other command or shows an error.
If the command prompt suggest you to type something else, then type that. It will work.
If the command prompt shows an error, then please post the detailed error here.
Information: You might want to check this app