Step 1: Tap and hold the file you want to delete. (To delete multiple files, after selecting a file, check the circles next to each additional file you want to delete).
Note: You can only delete 200 files at a time. If you need to delete more than 200 files at once, go to OneDrive.com.
Step 2: Tap Delete OneDrive delete file .
Step 3: When asked to confirm your deletion, select OK.