Currently, TeamSnap Tournaments is a separate site from your regular TeamSnap account. You can log in at tournaments.teamsnap.com to access as an administrator using your TeamSnap credentials if you already have a regular TeamSnap team or sports organization account, and will be the same for both the tournaments web and mobile apps. Tournament participants will create their accounts and log in at events.teamsnap.com.
Wondering if you can use the same username and password? Read more here: Can I use the same login for TeamSnap Tournaments that I use for TeamSnap?