If you are just starting out working with Premiere Pro, but have completed some basic video edits, it is time to move on to your sound editing. When used correctly audio (including voice, effects or music) can be a powerful addition to your movie. One very simple way to transition between clips or effects, is to fade in and fade out. You can easily do this using the Timeline panel.
Open your project and select the track that is to have its audio faded in or out, by clicking on it with your mouse.
Expand the audio track by clicking the triangle to the left of the track's name.
Open the Audio Effects panel by clicking on the Audio Effects bin. Expand the options in each bin by clicking the arrow next to each sub-folder.
To fade in audio, drag a transition from the Effects panel to the Timeline panel. Drop it directly at the In point of the audio clip. You may also Double-click on the transition from within Effects Controls, and choose "Start at Cut."
To fade out in audio, drag the transition directly to the Out point of an audio clip. You may Double-click the transition from within Effect Controls and pick "End at Cut."