Here are three different methods for converting your wav (audio) file into a an mp4 (video). A wav file contains only audio, so when converting to video, you need to consider what the visual portion of your video will look like.
If you require a specific look from your video, you'll need to either use some video editing software on your computer (such as Premier Pro87, After Effects97 or Final Cut85) or you can use a web application like Audiogram33. Video editing software will give you the most flexibility and control over your output, but comes at the cost of a steep learning curve, and significant time investment (if not already familiar with the software) to create.
An app like Audiogram33 will let you upload your wav file, and quickly create your visuals by customizing on of their themes to fit your style. Audiogram33 can also transcribe your audio and add captions to your video that highlight as words are spoken (think karaoke), as well as place an audio waveform on your video. Audiogram doesn't require the technical knowledge or time investment that a traditional video editing suite would require, but can still create an engaging and professional looking video. View an example audiogram below:
Audiogram is free to use, use the following link to Get Started33
Finally if you don't require your video to have any visuals, you can use one of many available online file format converters to change your wav file to an mp4 with little to no effort, however your video will simply be a black box. Try one of the links below for a simple conversion tool: