Normalizing audio is done using Premieres “Audio Gain” window. Once the desired audio clips are selected, choose Clip > Audio Options > Audio Gain. From there, you can adjust audio gain along with max peaks.

For a tutorial on how editing audio in Premiere, click the Lynda playlist down below.

Lynda Playlist: DLL Adobe Premiere Audio Editing:
https://www.lynda.com/SharedPlaylist/8ddc8016741c429da14549b757d0a5d8