you will see tiny screws on the side or looks like the bottom for your card (do not touch the screws with springs they hold the heat sink ) of the cover remove them carefully then proceed to lift the cover up you will be able to use can compressed air to blow it out and the put cover back on and reinstall the screws back in but do not over tighten them good luck and welcome also enjoy your new cards I clean my cards at least once a month
 
I found this I hope it helps http://www.youtube.com/watch?v=EKbBOBK6m9M just keep in mind your not removing your heat sink just getting in to clean the fan and blow dust off the heat sink okay
 
but just remember your card is smaller with a added extension for the fan cooler I believe compared to my 670 and 680 which are are on full pcb board the 650ti boost is a smaller pcb board