In your Forever™ Account you can remove files from albums and tags, which will remove the files from that album or tag. Removing files from an album or tag DOES NOT remove them from your Library though.
You can only permanently delete files from your Forever™ Account from within your Library.
To delete a file or files, you will need to navigate to your Library. You can then either click on a file to bring it up larger in the file viewer, or you can select a file by clicking in the upper right hand corner of its thumbnail image.
If you are in the file viewer, you can click on "Delete" along the top, above the file image. If you are in the selection state, you can select either one file or multiple and then along the top you will see the option for "Delete".
When you click "Delete" from either of these locations, you will be prompted with a message asking if you are sure you want to delete. By clicking "Yes", that file or files will be permanently deleted from your account.