SQL Server 2012 installation, just like any other software's, is pretty straight forward. If you read
[Only registered and activated users can see links. Click Here To Register...] you will understand how easy it is to do and you will be able to do it yourself.
Don't forget to uninstall your current SQL Server version before installing a new one.
Also, this isn't a Shaiya related question, so searching for this on Google or YouTube would have given you more results.