It depends on the mobile you have, whether it accepts wav or Mp3. Most of the mobile accepts Mp3 format. Any editing and converting software will be of use. suggests to try
FlexiMusic Wave Editor. Play and record the audio files in the software then using "Save As" command convert and save the recorded audio files in the format of your choice (either as Mp3 or wav files). Then upload the saved file format as ring tones in your mobile.