You can upgrade your membership level by logging into your account and then going to the subscription tab. You will then select on the upgrade

You may cancel your membership by  logging into you account and then going to the subscription tab.  You will then select cancel.

You may update your payment information by logging into your account and then going to the subscription tab and then update payment.

You will see your perks once you logged into your account.  Mostly will be seen within your dashboard.