What kind of questions can I ask here, and how does the site work?
As a demonstration of how plan uploads specifically will work, you'll notice the question above has an execution plan attached (in Plan Explorer's .pesession format). I created this question by first uploading a plan from within Plan Explorer. You can download the plan, open it in Plan Explorer, and see that the toolbar will show a link to this question. If this were a real question, Paul White (blog | @SQL_Kiwi) would have probably already answered, telling me why my CROSS JOIN is so inefficient. 🙂
Note that this functionality is fully supported in both Plan Explorer FREE and Plan Explorer PRO. I provided some more details about the feature and the site in a recent blog post.