If you go to the "tools" menu, there should be an entry there called "startup". You can select whatever form you want to auto open when the database opens.
For making it read only you have a few options. Go to Tools menu, security, decrypt/encrypt
Tools, Database Utilities, Make MDE file. (This way your uses couldn't see most of your code)
If the file is on an NT based machine just set the file permissions to read only.
Before you play with some of the features though, you better make a backup. The MDE option strips out and compiles all the editable code and is non reversible.