The IDTool (Roaming Client) software needs to already be installed on your computer, and you need to have previously "activated" your account. (this occurrs by following the mailed instructions after your application was approved.)

Whenever you access a web page, using Internet Explorer, that requires a digital certificate, your computer will normally ask what certificate you want to use (in many cases, it will only list your one certificate).

If you were already logged into the IDTool software, then your certificate will be automatically used by your computer. If you were not already logged into IDTool, then your computer will open up IDTool, and ask you to log in.