In a nutshell
Assuming you can hear the streaming audio and can see the loop numbers in your audio player (see the FAQ if you can't) then it's really very simple:
- Listen to the music, until...
- ...you have an opinion about what you are hearing.
- Look at your audio player and remember the loop number.
- Click on the button as appropriate (e.g. "I like it")
- Then click on the loop number you remembered in step 3.
- Go to step 1.
The music will slowly evolve.
It helps to use an audio player which can be minimized, as in the screenshot below. This means you can carry on working/browsing/chatting while the music evolves.
If you just miss the loop number, you can still click "I like it!" or "I don't like it!" and the loop number you missed will be just underneath the currently playing loop. They are listed most-recent first.