From the Learning App Author page, you have two choices for editing Apps after they've been published.  After clicking on the App you wish to Edit, select of the following Edit options from the dropdown menu under the Actions tab:

• Edit for minor fix
• Copy as a new version

When you edit for a minor fix, you can change any content that already exists in your app, but you cannot add new pages. This is best for fixing typos or other small edits. Whatever you change will be pushed to all students immediately, so be careful what you change.

When you copy as a new version, you can edit or add content as you like, but you'll have to re-submit the new version to be published. Current students won't have access to the new version until they're done with the old version, and all future students will only be able to see the most recent version.