1. Go to Services and where Google+ is listed, click Add.
2. If you’re not already logged into the Google account set to manage the Google+ Page you’re looking to add, you’ll be asked to provide the login details for the account you want to sign into. Please note: you will need to provide the login details for the Google account set as admin for the page and not the Google+ Page login details. You’ll then be asked to accept the permissions required by Google to set up this service. Please ensure to allow all permissions when prompted.
3. Give the Google+ Page you’re setting up a name for your reference (this is helpful if you’re adding multiple Google+ Pages which have the same name but represent different locations).
4. From the dropdown menu, select the Google+ Page you want to set up the service for. If the Google+ Page you’re looking to add is not appearing in this menu, please check you’re signed into the correct Google account and that you’re looking to add a Google+ Page and not a Google+ Profile (these are not currently supported). For help with this, please see this page.
5. Select the type of feed you wish to see in the Inbox (this will be added in addition to the option to post to that Google+ Page).
6. Select whether or not you want to use Google’s link preview when posting to that Google+ Page.
7. Select how you want images to be handled if you include multiple images in the same post to Google + (currently only one image can be included in the same post if you’re posting to Google+ via a third party like Sendible).
8. You can then choose how you want to receive alerts for new activity on that Google+ Page or you can choose not to receive alerts.
9. When you’re happy with the settings, select the Save Settings button. You will then be able to select that Google+ Page to post to in the Compose box and a Stream will be selectable for that Google+ Page in the Inbox.