Borrowing a license?

So there are tools that I want to use that require a different license than the default license I have on my desktop computer. Using ArcGIS Administrator I can "borrow" a Spatial Analyst license and I have done that. My problem is I don't know how to let ArcMAP know that I have the SA license so that it will allow me to use SA tools. I thought it would be automatic but I guess it is not?

Any tips?

Thanks everyone :)