If you are starting with Windows Phone 7, welcome. Here is the little secret, most writers assume that you are not a beginner, but rather have some knowledge about the emulation environment, etc.
So if you want to use the Accelerometer simulator or Accelerometer emulator, here is how you do that:
Then you drag the red dot (which might see obvious), or you can shake the phone.
Although the performance is less than the phone, it seems to map pretty well to the phone.
Hope this helps out.