To delete a file from your SpiderOak network you will first want to navigate to the 'View' tab within the SpiderOak application. Next, open the tree to the file (or folder) you would like to delete and select or highlight it. Finally, click on the 'X' button in the menu bar to remove the file. Once you complete this step, a pop-up message will appear asking if you would like to remove this file from all future backups and – depending on your desires – make the appropriate choice.
NOTE: Please keep in mind that deleted files will not be removed instantaneously. For example, if you have other items waiting to be uploaded in the Queue (on the 'Status' tab) then you will have to wait for these transactions to complete before you notice the file deleted from your SpiderOak account and thus freeing up space to store additional items.