ODBC (or Open DataBase Connectivity) is a driver that allows connections to multiple databases, MSSQL being one of them.
You do not need to set up ODBC (at least not in my experiences), as it comes built on top of your preexisting OS. The additional configuration (Setting up the driver for ODBC -(Connection)> MSSQL) is done during the correct setting up of the MSSQL Database. Now, connecting through ODBC is different from the native MSSQL functions they dropped. First, you use a connection string, instead of a host. This you can see in the .rar file you mentioned.
Using the PHP Help site itself (

)You could attempt to understand how to use it. Try comparing two files, one using the MSSQL Functions, and one using the ODBC functions. Look at the PHP Manual I linked and compare. You'll find it'll be quite easy to convert your own from that, with slight reading.