To upgrade any version v4 to any newer v4 (for example if you upgrade a pre-release 4.0.1 to a later 4.0.3) then you do not need to copy or migrate any database. (That process is only required when migrating from version3)
There is no special/separate upgrade/installation file. Simply download and install the full version from the miniMrp website and if you already have a full version of miniMrp4 then it will be upgraded automatically when you install the newer version.
The newer version will install into the default program folder
(On 64bit versions of windows the default folder is C:\Program Files(x86)\miniMrp4 )
If you have installed or moved the software to a different location - for example to a shared network drive/folder - then you can change the install path to the other location.
Network/Multi-User - If all current users are already using version 4.0 via a shared network folder then you only need to install the new version once into the shared program folder and all users will automatically upgrade the first time they use the new version from the shared folder.
I M P O R T A N T : You should always backup your data before installing anything.