You can change the Currency your account is set to through the Account Settings page. The Account Settings page is accessed by clicking on your user's email address found in the top right corner, and the clicking on the Account link.
To change the Currency your account is set to, click on the pencil button next to the Currency field to open the Edit Account Currency window.
Select the Currency you would like to change your account to from the drop down menu, and then click the Update Account button.
Note: The label applies to all accounts, even if two accounts have different currencies. There is no conversion taking place.