Hi,
very exciting news!!! As a heavy and frequent reddit user, I want to give you some overview...
Reddit can be very confusing and overwhelming at first. But in its essence it is remarkably easy to use. Reddit is a social networking and news site, which is incredibly effective in aggregating interesting and new content.
They are thousands of different subreddits, which means topics, where people can post news, information, articles, pictures, vids and more. Some examples are worldnews, europe, science, pictures, germany, space, atheism and so on...
People can up or downvote both new threads and new discussion entries. You can see two small grey arrows in front of any entry to do that.
One of the most frequented subreddits is AMA (Ask Me Anything), where a lot of popular people answer questions. Like Bill Gates, Obama or Jennifer Lawrence.
Science AMA is another version of that.
What you need to do to ask Mady Hornig some questions tomorrow is creating an account and very importantly to upvote the AMA and questions you like.
The reddit crowd (especially in the science subreddit) is usually very sophisticated and well behaved. Of course some trolls will comment. Just ignore and downvote them.
Enjoy, I will def ask some questions tomorrow!