How to test a page with WebPageTest where the login is from a popup?

How can I test a page where I need to login through a popup? I am trying to do a performance test on this page:
http://store.nike.com/us/en_us/

Now how can I test the login functionality through webpagetest where the login pops up.

I am trying to use a script like this:

logdata    0
navigate      http://store.nike.com/us/en_us/
setValue    name=emailAddress      myemailaddress
setValue    name=password          myPassword
clickAndWait       value=LOGIN
logdata    1
navigate      http://store.nike.com/us/en_us/

Solution

I inspected the elements required to login and got the identifiers.
Then changed the code according to the following and things worked perfectly for me:

logdata 0
navigate    http://store.nike.com/us/en_us/
sendClickAndWait    class=login-text
setValue    data-componentname=emailAddress [email protected]
setValue    data-componentname=password yourPassword
clickAndWait    value=LOG IN
logdata 1
navigate    http://store.nike.com/us/en_us/