Please refer to the steps below to standardise the audio level of a song:
1. Click Edit on the track panel
2. Click on the desired song and click Normalization.
3. Drag the slider to the left/right to set a standard audio level.
Dragging the slider to the left lowers the standard audio level while dragging it to the right increases it.
4. Click OK.
The song is now normalized in accordance with the audio level that is set.