Accounts
On the top right part of the Playground main view, it is placed the account button 
that allows you to open the account info, including profile and environments management. Once opened account window, right next to the title, there is an account dropdown selector for the user to choose which account to work with.
Environments management
The environments tab allows to manage the environments of the selected account. At first sight, there is an environments list on the left and an information card on the right. Also, there are two buttons, above the info card, that enable to refresh the environments data and to create a new environment. On the list, the environment in use is displayed with the aquamarine border color. If no environment selected from the list, the info card shows a summary of all the account environments quotas.
Environments summary
In the following section, working with environments there is a much more detailed description of how to deal with managing them.
Plans&Billing
The last section of the account window is the Plans & Billing section where the user is capable to perform actions like updating the billing, checking the invoices or upgrading the plan.
To know how to execute those actions, check the Subscription section where you may find information like how to change the current plan or how to apply a discount.