To delete a file, click on the x on the right side of the screen when you hover your mouse over the filename.
After you delete the file, it is placed in your ownCloud Recycle Bin in case you need them again. These deleted files will contribute towards your quota (even if the quota message suggests otherwise). Once the files in the Recycle Bin exceed 50% of your quota, the system will start to delete files from this section, starting with the oldest files first. To manage your storage more effectively, you may wish to permanently delete some items from your Recycle Bin to ensure that other files will not be deleted automatically.
After you initially delete a file, it will be placed in your ownCloud Recycle Bin. If you wish to restore the file to it's original location, follow these steps: