I apologize you were unable to see these options as easily as you should! When you view the social share section of your email campaign, do you automatically see the post calendar on the right hand side?
If this calendar is already showing, then the Calendar button under options will not be available. With that said I can see you were also able to speak with our phone support about using Social Share as well. Are you still in need of assistance? As for submitting your feedback, if you can please share a screenshot of your pop-up we would be happy to look into this further for you.