You can set the "Log in using" Account name and password in that dialog box.
But if you do that, what is the point to:
I have user name and passwords set up for different users.
I have the filemaker file on one computer that will act as the "server". I have it to where the computer starts up and filemaker will start. I would like the password and username automatically log in. But on the other 3 computers they will access it through filemaker program so they will need to log in using their username/password which I want them prompted to do so. I hope this makes sense.
If your host computer is a Mac system, set up Keychain to open Filemaker with a specified account name and password.
If it is a windows system, put a second Filemaker File on that Host computer with the same account name and password defined that you want to use to open the file on the Host computer. Set up File Options on this additional computer to automatically open the file with the account name and password. Also set up OnFirstWIndowOpen in File Options to run a script that opens the original file. This script, which needs only an Open File script step, will open the original file with the same account name and password that you specified in File Options for the first file.
Then, to open the hosted file without needing to enter an account name and password, double click this "opener" file.