as strumminsix said, you would normally convert to a WAV for editing. however, WMA is a compression format and I have spewed on this a number of times before. If you convert to a WAV, you will uncompress and will definitely lose some fidelity when you compress again, say to an MP3. This unless the recording device used the WMA lossless algorithm.
A quick search on Google yields a bunch of conversion utilities from WMA to WAV, MP3 and other formats.
Audacity is a GNU freeware program that can do editing of WAVs, MP3s and some other formats. There may be other free ones also.
And there are lots of shareware programs that can do same, maybe with more features, easier to use, etc. I happen to have purchased Goldwave from before the days of Audacity. It happens to be able to load WMA files as well as WAV, MP3 and others. I have never edited a compressed file before, though.
I would try to convert to WAV or MP3 and then edit. Good luck. Let us know how it turned out.
The river keeps a talkin'