One easy thing to do is to normalize that event (right-mouse-button click on it, switches, normalize). This will make that event as loud as possible. You can then drag the top edge of that event down to reduce the volume if necessary. Unfortunately if you have any loud peaks in that event then this method may not gain much. In that case, you can Split the event just before and just after those loud peaks and then normalize the rest of the pieces individually.

A better method is to use a volume envelope (Insert / Envelopes / Volume, or press V). A thin blue line will appear through the middle of the entire audio track. Double-click on this line just before the event starts, just after it starts, just before it ends, and just after it ends. You will see four little nodes appear on the line. Drag this line up inside the event to raise it's volume. You can add as many points as you like to continuously adjust the volume throughout the track.