For Site Browser Users
Click your name in the upper right hand corner of the page. Go to My Account and click Change Plan under Membership Details. From there, select a new plan and click Next before confirming final details. An upgrade will be effective immediately.
For App (iOS/Android) Users
Click More in the lower right hand corner of the page on iOS, select Membership Details followed by Change My Plan. From there, select a new plan and click Next before confirming final details.
Plan upgrades take effect immediately. Plan downgrades take effect at the start of your next billing cycle.