If it asks for one, the "puzzle" has truly begun. Check the source where you found the link—often the password is the URL of the website or a specific username.
Right-click part1.rar using WinRAR or 7-Zip and select "Extract Here." Puzzle.part1.rar
Technically, "Puzzle.part1.rar" is a classic social engineering tactic. Humans are naturally curious; we see a file labeled "Puzzle" and we want to know what’s inside. If it asks for one, the "puzzle" has truly begun
If you actually have this file and want to see what’s inside: If it asks for one