Use the morphs in the clothing- breast size, hip size, etc..  (the dials).  Sometimes the clothing morphs that come with the clothing are enough, sometimes not.  I personally purchased PhilC's Wardrobe Wizzard 2:

www.philc.net/WardrobeWizard.htm

This allows you to add any morph from your human figure to the clothing, in order to get a perfect fit (you will still have to use the morph dials, but sometimes more morphs will allow a better fit).  With Wardrobe Wizard you can also convert clothing from one figure to another.  There are also a few here on renderosity that I have not used, but work just as well I am sure (and at a lower price than Wardrobe Wizard):

http://www.renderosity.com/mod/bcs/index.php?ViewProduct=64629&

You can also use magnets in Poser, but as a newbie that may not be the way you want to go.
(Poser menu -  Object*Create Magnet). 

Your clothing does not look too far off, and you can most likely make it fit with the morphs supplied in the clothing (dials).  Start with Breast size, and hip size/width, and play around with the dials a bit to see what they do.