Error with StateManager and Interfaces

hey, Im trying to follow this unity programming book. I get an error like this:

Assets/Code/States/BeginState.cs(6,22): error CS0738: Assets.Code.States.BeginState' does not implement interface member Assets.Code.Interfaces.IStateBase.ShowIt()’ and the best implementing candidate Assets.Code.States.BeginState.StateUpdate()' return type void’ does not match interface member return type `void’

Just implement the named method (ShowIt) ? In MonoDev right click on the used interface next to your class declaration.[30705-screen+shot+2014-08-10+at+23.31.34.png|30705]

ok thanks it worked