Okay, so I need to know how to share posts. I used the icons to share via Facebook but it didn't register! Do I have to wait a while? Please, I would like an answer. :D
To share a post you need to either copy and share with your friends the link which appears when you click the "link" button under the question, or you can use the built-in mechanisms for publishing via Google+, Facebook and Twitter, by clicking the appropriate buttons on the left of the question.
For the purpose of the currently-running Mass Effect 3 promotion, you need 5 different people to actually click on the link you have shared, in order for it to count as a shared post. The post also needs to have at least one upvote.
You can see this information (and more) under the contest rules (click the "contest rules" button on http://me3missions.com/):
For post sharing: use sharing buttons embedded in the question page on the left side or the permalink below the question. Shared posts should have a score greater than 1 and at least five click-throughs on the shared link.