Having trouble sharing posts on Google Plus

This should help:
http://jetpack.com/support/publicize/google/#privacy

You can find the “Settings” option on the left of the Google+ home page:
http://i.wpne.ws/fRhI
https://plus.google.com/

Here is a direct link:
https://plus.google.com/settings

Once you’re on that page, the link to switch to classic Google+ is at the top:
http://i.wpne.ws/fRJY

If you’re trying to change settings for a Google+ Page, you’ll need to switch to that page first. You can do so by clicking on your profile picture in the top right corner of Google+’s home page.

I hope this helps.