Bungie.net on a Web browser, not the app. Then in the upper left corner select my legend, then choose progress. At the top where you see your character you can click on it to change it to whichever character you want to collect fragments with. Then scroll down and you'll see the ones you've collected and which ones you're missing. Mark down the Roman numerals of the ones you're missing and Google them or go to destinycalcifiedfragments.com