Download Audacity.
you can then open other sounds from other files, and look at them in there. You can learn from it, but ill spoonfeed ya:
1. Open your .wav file in audacity
2. Cut it down to the length you want (if you need to). This can be done by clicking and dragging the part you would like to delete on the timeline
3. go to the side of the timeline with the dropdown menu and everything.
4. click the arrow that points down.
5. "Split Stereo Track"
6. Change the "left" and "right" to "mono" on both of them
7. on the second one, click the "X" button next to the drop down
8. File --> Export
9. Make sure all the spaces are filled with underscores when naming it.
10. Locate it, and you can use it!!!