Linking the two accounts is something many TwitchCon goers (will) want to do, some for no other reason than to have their Twitch handle on their badge rather than their real name... hey, whatever works! But it's possible to check whether or not your account is currently linked, by simply logging in our site, clicking on 'My Tickets' then the 'Details' button. If a Twitch account has been linked it'll be found/displayed here, and if not a huge purple button marked 'Connect Twitch Account' is your next step.
Please note that at the time of writing (October 3rd, 2017) there's not yet a way to switch existing accounts; if one is already linked, you'll not be able to swap it with another one. Not yet. 😁
Regarding 'Chat Badges', after linking the accounts if you still don't see the badge, head back over to the Twitch site, click the COG wheel below your chat box, then "Edit Appearance" and you should see the badge there.
This thread on Twitter has been useful to a fair number of users already:
Please also note that badges may not always appear immediately, as communication between the two systems happens periodically rather than constantly.