Step 1: Find someone who is already on Google plus.
Step 2: Your friend should add you to a circle like “friends”
Step 3: Ask him to upload a picture or add a status message and share with you by specifying circle name at the box at the bottom.
Here in this demo, I have added my friend who is not using Google plus to a circle called “friends” and shared a post with him.
You can notice a checkbox at the bottom “also email the person not using Google+”
This will trigger the notification to you and next time you enter http://plus.google.com you will be able to use it.
Update : Install the Google plus extension on Chrome and access Google+ through the extension.You will be directed to Join Google+ page [ this is working for some people]
Please let us know your comments.