Anytime you add a .wav sound file or a .mov or .wmv video file to to a PowerPoint presentation you need to copy those files into a folder with your PowerPoint presentation. This groups the files in one location so they can connect to one another and your sound will play in your presentation later.
To add the .wav sound file to your PowerPoint presentation create a folder for your presentation and save your PowerPoint presentation in the folder. Next, right click on the sound file you want in the Clip Organizer and click copy. Now right click on your folder and click paste. The .wav sound file has now been added to your folder. Now go back to the slide where you want to insert the sound. Click Insert> Sound>Choose Sound from File>Find and select the .wav file in your folder>Click OK. A pop-up window will appear and ask you how you want the sound to start in your PowerPoint. I tell students to select "When Clicked". This lets the student start the sound when they click the slide instead of it playing automatically when the slide comes up in the presentation.
To try out the sound on your slide from your Powerpoint presentation, click the Preview button on the ribbon.