What you need to do is install on each machine and set the default directory to a mapped drive or in this case File.
The plain Vanilla Quick Books doesn't support this type of thing but the Pro version does and with that from the master install you can decide what services are available to each user.
So you can have one person entering in expenses like advertising, petty cash and other general expenses, another doing wages and the like and then the master computer has access to everything. You do not want your data entry staff to have access to the wages of the entire staff so you need to establish some rules here.
If you have the Quick Books Payroll version it's all in the destruction manual on how to set up the various rules but what it doesn't tell you is how to relate all to the one data file. So what you need to do is create the various accounts on the Master Computer which is holding the main Quick Books File and then on each computer that is accessing the file you need to create the accounts that they will use to access the Master Data File which incidentally doesn't need to be on a computer with Quick Books actually Loaded you can create everything from the computer where you originally installed the program and this is always the one which has all the privileges. After you install and setup the necessary parameters you can then chose to move the file to a remote computer but make sure that is it one that is constantly backed up or you'll be defeating your DR Plan with some very expensive data to recover if worst comes to worst.
Once this is finished you can then go to the other 2 computers and link them to the Master Data File and create their user accounts. If you don't do it this way every computer will save the data locally and it will not be a workable solution as you'll have 3 data files that can not be merged with each other so you'll need to reenter all the data again once you have the system setup correctly.
Col