SQL Server Cluster running two instances

Hi,

I have SQL Server Cluster running with two sql intances. SQL server 2008 r2 and Sql server 2012 r2 and current version is

SQL SERVER 2012 r2

Microsoft SQL Server Management Studio11.0.5058.0
Microsoft Analysis Services Client Tools11.0.5058.0

SQL SERVER 2008 r2

What is the best practice to upgrade the Cluster SQL CU?

Regards,

Mohammed

Please remember to mark the replies as answers if they helped. Br, Farhan