If by 'pick up the sound' you mean 'make it louder', the tool you would use is Amplify and it is found under the Effects tab.
If you wish to amplify the entire file, right click on the file, and click on "Select All." This will highlight the entire file.
Then click on the Amplify button, which will bring up a dialog box, where you can select a 'percentage' of gain, then click 'Apply '.
100 % will leave your file as it is. Use a higher percentage to raise the overall volume (amplitude) of the file.