Sewing help!

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 Hey,
So...I'm making this dress for my graduation, but I've left my handy dandy patternmaking book at home (eg. miles away), and I'm a bit rusty in this department these days, so a little help would be appreciated!

This is the pattern I'm working from:

This is what I'm trying to do (skirt portion only)


 

sorry if it's hard to see, I'm in a bit of a rush, but basically what's the easiest way to go about achieving that nice little drapey thingyamee on the right of the dress? I mean...the logical way would be to just extend the front and kinda wing it? I don't know...it seems ridiculously simple but I can't seem to figure it out. Thanks in advance!