You need to explain better and provide proper technical info. Provide a screenshot of the timeline, system info, version of AE and so on.
You probably need to increase the length of your composition. Edit>Composition settings
You need to start with the basics. First select the audio file in the composition panel and check the properties by looking at the top of the Project Panel and determine the type of file and the length of the file. Second, check the composition settings to see if the length of the composition matches the length of the audio file. If that does not solve your problem then you need to explore the AE UI and learn how to use the tools.
Type timeline in the Search Help field at the top right corner of AE to explore the community resources that explain how to do things in the timeline. Use the search help field to find out how to change the end point of a layer by typing something as simple as change out point in the search help field.