Over the track view clip pane press "T" or click the middle mouse button. This will bring up the HUD with the edit filter toward the right of it. As ProjectM has already said there is also a widget in the Track View header area but you need to make sure the widget manager is set to display it there.
From the edit filter select clip gain. You'll now be able to adjust clip gain using the envelope. Click drag on it to create and adjust nodes if you don't want a straight adjustment.
To create a fade, click drag toward the top right or left corner of a clip where you'll see a red line appear and the cursor change to the fade cursor to indicate that click dragging will create a fade. Fade type can be adjusted using the TV---->Options---->Crossfade type menu choices.
And finally I have a video on my youtube page explaining the
edit filter. There are others there you may find helpful and I also author more detailed videos that you can buy from either
SWA or the
Cakewalk store HTH