A possible first step that is extremely simple is to right-mouse-button click on the audio event, choose Switches / Normalize. This will raise the highest peak in the event to 0dB. If your entire event is quiet then this will make it as loud as possible and you can easily reduce from there.

If you don't like that idea then you can Insert / Volume envelope which will allow you to raise the sound up to 6dB and additionally let you vary the sound from point to point along the event.

I doubt you want compression. From what you've described it seems like all you need to do is raise the volume uniformly without altering it.