Accessing your Google Plus user ID is simple:

1. Log in to Google+.
2. Click on the “profile” tab to view your own profile.


3. If you look at the URL in the address bar, it should look something like this:

   https://plus.google.com/113551191017950459231/posts
   

4. The long numerical string in the URL is your Google+ ID. Here is mine from the URL above:

113551191017950459231