You access the Developer Studio features from the Developer Studio Dashboard. Click the Developer Studio menu and choose Open Dashboard.
When the dashboard appears, you can scroll down to see links to all the Developer Studio features. Click a link to create that item.
In addition to using the dashboard, you can choose File -> New -> Other and select an item from the WSO2 category.
If you have an existing project, you can right-click the project, choose New, and then choose one of the WSO2 options from the menu.
For an introduction to working with Developer Studio, see Quick Start Guide.