Download and install the SQL server from Microsoft for your OS. Then change the primary database name to be "PreRollPost"
Sorry, Microsoft doesn't make this very easy! Assuming you are a full Admin for your computer, and you're running Windows 10 this should work.
The link https://go.microsoft.com/fwlink/?linkid=853016 takes you to Microsoft's SQL Server 2017 download page.
Scroll down and choose Express Edition (it's free). Run it and choose Basic installation.
When it gets to the end click CUSTOMIZE.
Then keep clicking Next on the SQL Server 2017 Setup until you get to the INSTANCE CONFIGURATION.
Select Named Instance and type in PREROLLPOST then keep pressing Next until finished.
Restart computer for the new database to take effect. Then run PreRoll Post application and check if it has connected properly.