Simplify the following text for a Grade 9 native English-speaking person.
Original: In case you did n't know , when you add content to talk pages and Wikipedia pages that have open discussion , you should sign your posts by typing four halfwidth tildes ( ~ ~ ~ ~ ) at the end of your comment .
Simplified: Just in case you did n't know , when you post messages on talkpages and Wikipedia pages , you should sign your posts by typing four tildes ( '' ~ ~ ~ ~ '' ) at the end of your message .