Before jumping into the details, some quesitons:
Do you know HTML and Javascript? That is, can you program a web page in those languages? If you can then you can do this yourself - if you can't then you'll have to hire someone to do it.
You may be able to figure out some things about the popup on your website - popups are done using Javascript so if you view the web page source code from your browser you might be able to see the JS source that postions the popup. Further, if you have access to the web page source code then better yet, you can can change those x,y values to 0,0 to place the popup in the upper left corner where you want them.
If all of that is too much for you, then you should just hire someone to do it - it's a very easy fix when you know HTML and JS.