In server 2008r2 you need to import the power shell modules before using them, for example to run any failover cluster commands you need to import the failovercluster module (This is not true for server 2012, new post to follow). Typical PowerShell there are a couple of ways of doing the same task but here is the one I normally use.
– Displays LOADED modules
– Displayes Modules that can be loaded
In the example below I imported the failoverclusters module in Server 2008r2