Since you did npt provide the version number, Microsoft has this information listed on their website: https://support.microsoft.com/kb/170961
This will give you the information you need to change an Access Database Password.
Or follow these general instructions for Access 2007:
Open Microsoft Access 2007. Click on the Windows icon on the top-left corner of the screen. Scroll down and click on the Open command. Scroll through your computer folders to select a database. Click on the file to select it. Click on the down arrow next to the Open button and click on Open as Exclusive.
Click on the Database Tools tab on the top of the screen and click on the Decrypt Database button in the Database Tools group. Type your password in the Unset Database Password box. Click OK.
Click on the Encrypt with Password button in the Database Tools group on the Database Tools tab. The Password box should now open.
Type your new password in the box and click OK. Retype the password in the Verify box and click OK. The database should now recognize the new password.