Problem acess ajax toolbox controls from toolbox

Question

I am having trouble accessing the ajax control toolkit that I installed on my visual studio.net 2010 professional ide.
I followed the directions that are listed on the following link: http://www.asp.net/ajaxlibrary/act.ashx.
I setup a new C# website and had the default.apx file open. I was then able to see the ajax toolkit controls from the NEW website I setup.
However now for an existing C#. asp web form 2010 application, I am adding a new page webpage and I want to use the ajax controls I just added to my ide. However, when I click on the toolbox, I do NOT see the ajax control toolkit I just added to the my visual studio ide from this existing project.
However when I go back to the new web application I just setup, I DO see the ajax control toolkit.
Thus I can see the AJAX Control Toolkit on the toolbox when I open the 'new' website project. However, I do not see AJAX Control Toolkit on the toolbox when I open my existing application.
Thus, can you tell me how I can access the AJAX Control Toolkit from the tooltox for my existing application?