Step 1: Select Cygnus from the "hero select menu".
Step 2: Select a map with a suitable staircase to fall from.
Step 3: align yourself with the aforementioned staircase.
Step 4: hold forward while mashing jump until you find yourself at the bottom of the staircase.
Congratulations! you are now tumbling down a set of stairs! well done!

I hope you enjoyed the guide. :)