I did some digging on that bike. Nice bike. Looks like you might have this fork:

http://www.xfusionshox.com/products/280-2012-vengeance-hlr-coil

There is a link on the above page to an owner's manual.

Also, fwiw, I found a review of your bike:

http://www.bikeradar.com/us/mtb/gear/category/bikes/mountain-bikes/full-suspension/product/review-specialized-status-1-14-47975/

Getting back to preload, normally I would expect to see it as a knob on the top left. Unless you have an air preload, in which case look for a Schrader valve top left.

Edit: I read the PDF manual. Looks like no preload. You might need to order a different spring then.