To sign in, click the "Log in" button in the top-right corner. You will get a popup explaining that you will get prompted with a list and you need to pick Internet Explorer in that list. This is currently a Windows issue, web browsers other than Internet Explorer don't allow a website to navigate back to an application, which is what we use to authenticate you.
A new window will appear with a login form. If it doesn't for some reason, enter this url manually in Internet Explorer:
Once you logged in with your SoundCloud or Facebook account, you will get a pop-up asking if you want to be redirected to the application. Click Yes.
You should now be in Clouder!, on your profile page