Windows does not provide a simple built-in button that adds a password directly to any folder. But you still have several free ways to protect folder contents. The best choice depends on whether you need a one-time archive, account-based privacy, whole-drive encryption, or daily folder locking.
This is the closest free method for adding a password around folder contents. It works best for folders you store or send occasionally, not folders you edit every day.
If each person has a separate Windows login, NTFS permissions can restrict who can open, edit, or delete a folder. It is useful on managed PCs, but less friendly on shared home or small-office computers.
The hidden attribute can keep a folder out of casual view, but it is not password protection. Anyone who knows how to show hidden items can reveal it again.
EFS can encrypt folder contents for your Windows account on supported editions. It needs careful certificate and account recovery planning before you rely on it.
BitLocker is strong when you want to protect an entire drive, especially a laptop or external disk. It is not the same as adding a password to one selected folder.