It's extremely important to know how to control how loud your music is going to be. If it's too quiet, you won't be able to make good judgements about how to make it better, especially when we get into mixing in Part V. If it's too loud, it can damage your ears. Your ears are the whole reason you're making music, so protect them!
NOTE
The steps for adjusting volume may vary according to what audio interface or sound card you are using. The following procedure will cover the majority of built-in sound cards, but some may have their own mixers or control panels. Such applets are usually found within the Windows Control Panel, which you can access via the Start menu.