If you have become addicted to Google+ by now, it is high time that you connect your other accounts like facebook, twitter, Yahoo! etc., to your Google+ account. By connecting them to your Google+ account, you can see in your Google+ profile relevant content that your friends share on the web on facebook or twitter. For example, if you like Lady Gaga on facebook, then after connecting facebook to your Google+, you would be shown suggested Lady Gaga profile to add to your circles in Google+ page. Here is how you can connect your facebook, twitter and other account with your Google+ account :
Step1: Go to Google Plus & sign in your account.

Step2: After sign in you go to Connect Account. Now
you can see like below image.
Step3: To add account Click on Connect an account.
Step4: For add facebook account select Facebook > Enter Profile URL > Click Add.