Open file with full access password.
Go to File Options. Specify the account and password in File Options that you want the system to use to open the file without asking for a password.
You may want to first go to Manage | Security and disable all accounts except guest and the admin account, removing any password specified there. Then use File OPtions to specify admin as the account with no password--this is the default setting for any newly created file that has not yet been password protected.
Note: When making changes to Manage | Security, it's a very, very good idea to make a back up copy before making any changes. Then, if you accidentally lock yourself out of your own file, you can delete that copy and revert to the back up copy.