The most straightforward way to move an application to the next stage is from your Applications dashboard. Clicking on the next stage in the application flow will trigger a pop-up asking you to complete or delete the outstanding tasks before moving the application to the next stage. Once you do that, the application will move to the next stage. If you want to move the application back to the previous stage, all you have to do is cli on the previous stage in the pipeline and the application will move back to the previous stage.
Here's how to do it: