To upload files to the common drive, you need to click "Common Drive" in the menu on the left.
First you select the folder you wish to upload the files to. If you need the files to be availble publicly, use the "Media" folder. If it's for members only, use the folder named after your club.
Select the folder by clicking it, and then click the "Upload" button in the top right corner.
You can now select one or more files you wish to upload to the common drive. Do this by clicking the button "Select".
When you have selected the files you want, click on the button "Upload". Now your files are being uploaded.
