The file explorer contains a special instance of Windows Explorer to allow you to easily find the files that you want to delete.

You can manipulate all the files and folders just like if you were working with Windows Explorer.
Once you find the files or folders that you want to delete you can right click on them and choose "Add Selected to Delete List" or simply drag and drop the files or folders to the delete list on the bottom.
There is a filter function that allows you to specify the type of files that you want to see.

To use the filter simply set it to the type of file that you want to see, if you wanted to see only text files you would set it to: *.txt
Press the delete button on the bottom right to securely delete all the files and folders in the listed in the delete list.
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