First you have to know how to make a selection:
To delete, cut, copy, paste your selection of sound, you can use the usual shortcuts (Delete; Control+X; Control+C; Control+V), or the Edit menu, or the following toolbar, with different options:
For example, the last one, the Mix and Paste command, mixes the selection you've cut on the clipboard starting at the insertion point. This allows for smoother transitions into the audio file.
But be carefull: all the changes you make in this waveform view are destructive!! If you cut a sound and save it, the file will be cut forever. So it could be safer to make backup of your original files...
Noise reduction takes a lot of work (trial and error) so don't get frustrated. Without professional equipment, getting the right amount of noise reduction while maintaining audio quality can be very difficult. Just try to get as close as possible: noise reduction is never perfect.
Go to Effects > Noise Reduction
You have 2 possibilities: noise reduction or hiss reduction.
You can also try the other noise reduction options:
You may need to play around with these settings to get the right effect you are looking for...
You can also add special effects to selections of audio by using the Effects menu. Here are a few options you might find useful:
Just test the different effects to get familiar with them...
When you're satisfied with the audio, choose File > Save As. Specify a location for the file, type a filename, and choose a file format. Depending on the format you choose, additional options may be available. To view and specify format-specific options, click Options. When you are finished setting options, click Save.
In general, Windows PCM format is the best choice for saving uncompressed audio, and either mp3PRO® or Windows Media Audio is the best choice for saving compressed audio...