SIRP requires a browser with HTML 5 and current TLS support to log in and use available features. A recent version of any of the popular browsers (Firefox, Chrome, Safari, etc.) should work fine.
Browse to the URL provided to you during SIRP on-boarding or you can just click Join Now in SIRP Invitation email.
You will be presented with a form to enter your basic details and set a password.
After you are logged in, you will see your default dashboard. You can customize the dashboard by adding a different set of widgets or create your own dashboard with a different set of widgets.