By default, start Best Folder Encryptor does not require a password. While you can set an Admin password for the software to protect it from being used by others without the correct password.
Start Best Folder Encryptor, click the Settings button. Check the option "Need password to use this software", and set your admin password in the pop-up window.
If you don't need this password, uncheck the option "Need password to use this software" and enter your admin password, then click OK.
Related reading:
How to completely decrypt a Full-encrypted folder?
How to open or decrypt an encrypted file and folder?
What if I am prompted with wrong password when decrypting a folder or file?