The emblem comes from a Triumph. If your account qualified a package would have been delivered to your Postmaster back when it was first released. Assuming you have no packages at the Postmaster available to open then you need to pull up your character screen, tab over to Triumphs, then select Account->Moments of Triumph category. The triumph is called Prismatic Inferno. If you don't see the Triumph then either you haven't opened the package or your account didn't qualify. If you believe you do qualify and didn't receive it then you need to find your post game carnage report here on bungie.net for one of the matches during the qualifying period. Keep in mind the website will show dates and times in your local timezone. The qualifying time period dates and times are all in the U.S. Pacific time zone, so you'll need to convert your local date/time to Pacific to verify the match qualified. Also, you had to have finished the match in question. If you had one qualifying match, but didn't complete it by either leaving it early or disconnecting then it won't count for the Triumph. Once you find the game here on bungie.net there is a little link that will appear on the match summary that is a link to the PGCR. Click that and copy the link and paste it as a reply here. The qualifying period you need to have played is: December 8, 2017 at 10am PDT through December 12, 2017 at 10am PDT.