If you are logged into your Google+ account then go to the top right hand corner of the page and click on the drop down arrow near your profile picture. After you click on the drop down arrow you will get a drop down menu with a view profile button. Click on that button and you will be taken to your Google+ profile page and your Google+ URL will be displayed at the top in your browser's address bar.
Copy that URL and go to your HubPages account and go to your my profile page. On your my profile page click the edit profile button. Go to the links section and paste your Google+ URL in the Google+ field. Then go to the bottom and save the changes. I hope this helps.