BuddyPress.org

im developing a new site with wp and buddypress and i want to insert some text into the activity text field to be there when my users start to udate their status. The text will just be a youtube embbeding shortcode to help users to embbed their youtube videos easily since my users dont know anything about shortcodes, the text will be something like this: [embed width="123" height="456"]paste your youtube url here[/embed]. Im using versions wordpress 4.5.2, buddypress 2.5.3. My website is foobhoo.com but it is still in construction, please help. My question is how to pre fill text into text editor on buddypress whats new text field to be there for every user?