Encryption "scrambles" the contents of a database so it's indecipherable, even by a utility program that an expert user might employ to see your database from outside of Access. If you are worried that password protection is not enough security, you might encrypt the database as well as password-protect it. You must decrypt it before you can use it again.
Only the Owner
If you are working in a shared file environment, such as a network, you may have access to files that you are not the owner of. Only the owner can encrypt a database file.
To encrypt a database, follow these steps:
Close all databases. This is important; you can't encrypt a database that is open.
Select Tools, Security, Encrypt/Database.
In the Encrypt/Decrypt ...