html to aspx

Using windows Exployer I copied and pasted an html page inside my project folder.
Using VS asp.net I right click on the  folder went to Add -->Existing item an add. ed
that page. Later i renamed to a .aspx I when I run the page in the browers its display ok
however I cannot access the asp controls in the toolbox.
I only see HTML component.

My question is how do I get to use the ASP components.