How do I install a NuGet package into the second project in a solution?

I'm currently working on a solution that initially contained one project (My.First.Project.Name). I've installed Castle Windsor by executing:

Install-Package Castle.Windsor

I've just added another project (My.Second.Project.Name) to the solution and want to install Castle Windsor into this project also, but when I run Install-Package Castle.Windsor again, I get the error:

'Castle.Core 2.5.2' already installed
'Castle.Windsor 2.5.2' already installed
My.First.Project.Name already has a reference to 'Castle.Core 2.5.2'
My.First.Project.Name already has a reference to 'Castle.Windsor 2.5.2'

So my question is: How do I persuade the NuGet Package Manager to install the package into the second project?