The basic of converting .wav to .mp3 is specifying an input file and an output file and press "OK" or such a button. I've used a program called CDEX to do it, but there are others also, as you found.
If the help in the program and tutorials you find on the web don't help you with a particular program, try another one.
I have a 64-bit, Windows 10 OS on my HP laptop. I recorded some voice text on my 'Audacity program, which were automatically saved as wav sound and xml files. However, when I tried to send either as an e-mail attachment, both failed. I understand the only way to attach a file to an e-mail is to convert it to MP3 files, but even downloading a conversion program like MP3 converter 1.9 or Format Factory or File Viewer Plus leaves me helpless. I don't know the steps needed to convert the files. Help!