I've found the extractor's user interface to be a little confusing so I'd recommend copying anything you're working on into a temporary directory and working on it from there.
1. Go to the PAK / LSV Tools tab.
2. Click the Package path "..." button and select a PAK file.
3. Click the Destination path "..." button and select an output folder.
4. Click the "Extract Package" button.
5. Wait for the extraction process to complete. Done.