Follow the steps below:
- Click this link (new version updated) to visit the facebook invite all friends extension.
- Add and install the extension in your browser.
- After installing the extension, you will see an icon in the top right side of your chrome browser.
- Now login to the facebook and go to the group page in which you want to add your friends. Now click on the icon which is added in the top right side of the browser.
- That's all. You will see that your friends are being added in the group.