Add a button, set its button name to Paypal. :)
Seriously, if you really want help, you need to exert some effort in explaining your problem. As some people said, help us help you. :)
Now, assuming that what you mean was you want some paypal functionality on your ASP.Net web application, there are many articles out there if you only use
Google[
^]. Here is one article that might be useful to you.
Use of the PayPal payment system in ASP.NET[
^]