Changing the volume of audio tracks in Adobe Premiere can be done in multiple ways. Command clicking the audio clip on the timeline directly will add keyframes to the volume. It can also be done manually however using the Effect Controls option on the top left window.

For a tutorial on audio editing, click the Lynda playlist below.

Lynda Playlist: DLL Adobe Premiere Audio Editing:
https://www.lynda.com/SharedPlaylist/8ddc8016741c429da14549b757d0a5d8