Navigate to your experiment, and then to the appropriate subject (in the tree view under "Subjects and files"). Click on the subject. The subject view is shown, including a blue button labelled "ADD NEW SESSION". Click this button.
Fill in the form (all fields). Click the "Files" tab to add folder or files from your PC. Click the black button: "ADD FOLDER" or ADD FILES" and select files from your PC.
Finally, click the blue button: "SAVE". A view of the new session is displayed, with a green notification message saying: "Complex session was successfully created."