To use markup, simply put certain symbols around your text in your post.
'''Text''' produces a strongly bolded text like so: Text
''Text'' produces an emphasized text like so: Text
**Text** produces a spoiler like so: Text
==Text== produces a header-like text like so: Text
An email field of the form "dice XdY+/-Z" will result in X Y-sided dice rolled and summed, with the modifier Z added, with the result displayed at the top of the post body.