When you open a file in a standard desktop application directly from SuiteFiles simply use the standard save feature to save all changes back to SuiteFiles.
If you open a file into the Office Web Apps it's important to know that there is no save button. The Office Web Apps have an automatic save feature - changes that you make will automatically be saved back to SuiteFiles for you.
Important Note: Any file that you download before editing will NOT be saved to SuiteFiles. A downloaded file is saved to your local computer and the changes are also saved back to your computer. You will need to manually upload the changed file back to SuiteFiles if you need the changes added back to SuiteFiles.