This article will walk you through the steps of inviting people on Google+. Google has always had this reputation of not being able to feel the pulse of the market and act accordingly; same holds true for Google Plus also. Sending out invitations to people on Google+ is not as easy as falling off a log. But, here’s how to do it:
• First you need to login to your Google+ account.
• Unlike Face book, you’d have to type a message you want the invitees to see and that message needs to go up on a new “stream”.
• The next step is to type the mail addresses of people you want to share the message with in the text box that says “Add circles or people to share with”.
• Once you’ve typed in the message, you need to click on the “share” button and the message would be sent right away to those people.
• The good part about this is that your message would not be visible to people other than those whom you want to see.
Once you’ve done the above steps, your friends will each receive a mail from Google+ with proper prompts to open a new account.

There’s another way of doing it also. Just click add new person on your profile, enter name and click save.