To manually upload just click 'Choose file' then navigate to the 'SavedLogs' folder inside your VAFS folder (?:/.../VAFS5/SavedLogs).

Select the relevant .xml file for that needs to be uploaded then click the 'Process This Flight' button. The process generally takes 30-60 seconds and when it is complete it will tell you that it has been sucessfully uploaded at the bottom of the process.