Change the instance type:
In the navigation pane, choose Databases, and then select the DB instance that you want to modify.
For Actions, choose Modify. The Modify DB Instance page appears.
Change the DB instance class.
When all the changes are as you want them, choose Continue and check the summary of modifications.
Choose Apply immediately to apply the changes immediately.
On the confirmation page, review your changes. If they are correct, choose Modify DB instance to save your changes.
Alternatively, choose Back to edit your changes, or Cancel to cancel your changes.