how do you delete a document?
This question is not related to LibreOffice but your operating system, which you did not mention. Consult your operating system’s manual.
Generally speaking:
- Open your file manager
- Move to the directory where you stored your file to
- Most likely:
Right click the filename -> Deleteallows to delete the file
More information: FAQ - Filemanagement
An addition to Opaque’s suggestion: you can just select the document (file), so it’s displayed in a different color than the rest, then press the Delete button.
You can select more than one file in the file manager: press Shift and select the files that you want to delete, or, after selecting one file, press Ctrl to select all files in a range, then delete them.
If you mean that you want to delete all text, just press Ctrl+A, then any typing will replace the text.