A couple ways to do this.
Method 1: Quick and dirty but destructive.
Select the audio clip then Process>Apply Effect>Normalize
That should set the loudest point of your clip to 0dB and adjust the rest of the clip in relation to that.
You could also play around with Process>Apply Effect>Gain and adjust the amount of volume change manually until you get what you're looking for.
Note that using the Normalize or Gain function is destructive. Meaning its going to change the audio in the clip. You can undo if you don't like it, but once you save and close your project, you will not be able to undo later. So if using these functions end up doing something bad that you don't notice right away like adding too much hiss or clipping off some transients for instance, you might not be able to easily fix it later.
Method 2: More difficult but often leaves you with better options.
If you want to bring up the volume in a non-destructive way, try using an EQ plugin followed by a Compressor in the FX bin. Raise the master level of the EQ by a few dB. If you get noise or hiss use the EQ to roll those frequencies off a bit. Then use the compressor to bring up the level even more.
Doing it this way you don't change the original audio at all. So if you decide later that you've compressed too much life out of the track, you can adjust the compressor settings as needed.
post edited by JohanSebatianGremlin - 2016/09/03 13:27:34