If you want to remove a file from your vault, you have two options: delete it or unprotect it.

To delete a file:

1. Long press the file to select it
2. Then tap the Trash icon at the top of the screen.

This permanently deletes the file from your vault, and also deletes the file from your device.

To unprotect a file:

1. Long press the file to select it.
2. Tap on the lock icon at the top of your screen.

Now the file is no longer safe in your vault, but you will still have access to the file on your device.