Are you just wanting to put items in the attic or insulate the items in the attic?

Compressing or altering the insulation currently in your attic will create a dead spot allowing hot air in the summer to enter the living area and cold air in the winter to do the same more easily. Look at the housing code in your area for the minimum R-value for your region of the country. For instance R-19 is for use in walls with 2X6 construction or abourt 6 inches thinck of insulation.

If you are just putting items in the attic you may want to build a small platform to store the items on. You could do a simple sheat of plywood across the rafters or a more advanced setup. However you decide to do it you need to know the rafter spacing and you may want to support the rafters with cross bars or spacers to prevent fexing and possible celling damage in the room below the storage pad/area.

Advanced would be 2X4's across the rafters (attached so they do not fall over and help stablize the house rafters) with insulation inbetween the 2X4's then lay the plywood on top and attach it to the 2X4's so it stays put.

PINK STUFF...
If you add the pink stuff are you talking pink fibergalss based blow in insulation or batts or rolls of fiberglass based insulation? If you are using batts or rolls you need "Unfaced" insulation (unfaced means it has no craft paper on one side.) since you already have insulation in the attic the faced or with paper type will trap moisture and may cause mold/mildew as it will not breathe (or it, the craft paper facing, is a vapor barrier when inbetween layers of insulation). The faced stuff is mostly used in walls for being able to tack it to the studs or otherwise attach it.

hope this ansers your questions.