Here are the steps to fix a cracked screen with nail polish:

1. Clean the cracks and dust with a microfiber cloth.
2. Apply a thin layer of clear nail polish over the cracks.
3. Let the nail polish dry completely.
4. Utilizing a razor blade, scrape off the dried polish.
5. Repeat the process if necessary.

Please note that this is not a permanent solution and it may not work for all types of cracks. It is recommended to take your device to a professional for repair if the crack is severe or if you are unsure about how to proceed.