Which version of Poser are you using?  If you have Pro 2014, then you have the fitting room.  If you have any version below this, then you do not.

However, every version of Poser from 8 up comes with Wardrobe Wizard.  Yes, you will still have to purchase the add on for V4 as WW only comes with support for Poser native content but compare what you've already spent on morph packages, it's not much.

WW can add whatever morphs you create in your figure to clothing in a couple of clicks.  It come with a walk through and PhilC's assistance is excellent.  Either through his forums or email.

Poser also comes with a morph brush and magnets that can help with adjusting clothes to fit morphed figures without having to spend any more money.

There is no right or wrong way when it comes to a workflow.  Everyone's workflow is unique to them.  You have to find what works for you and go with it.