How to set browser type and connection speed?

I’m trying to build a URL for testing but I’m having troubling finding how to pass the browser type and connection type. Currently I have:

http://www.webpagetest.org/runtest.php?url=www.testpage.com&private=1&fvonly=1&f=json&video=1&k=myapikey&callback=?

To this url I want to add the parameters for browser and connection, how would I go about doing this.
Thanks!

The docs here will help: https://sites.google.com/a/webpagetest.org/docs/advanced-features/webpagetest-restful-apis

But basically you need to specific the location, browser and network connection e.g. Dulles:Chrome.DSL, if you want a custom speed use custom instead on DSL and use the bwUp, bwDown, latency and plr parameters.

getLocations.php will give you the locations and browser combinations