Your team captain or the league manager has to add you to the roster in order for the team to show up in your account.
PRO-TIP: If you don’t see the team under your account, ensure that the team captain or league manager has added your e-mail address correctly. To check which e-mail address is associated with your account, go to Settings > My Account.
Do NOT create a team. This will NOT add you to your league team’s roster. A new team will be created but it will not be associated to your league.