Blu-disc studio lite is a nice free tool. A little difficult to use, but great once you get the hang of it. If you have an Adobe CC subscription you can use Encore. You’ll have to download it from the CC app and select the CS6 version of Premiere Pro.

You’ll also want to extract your audio and video streams from the MP4 container. However I don’t believe your MP4 will be that great in quality. You may want to go for a higher bitrate version lumped in an MKV container. MKV’s are much better to work with when it comes to authoring as you can extract the streams from them more easily.

You can easily convert your mp4 into an mkv using ffmpeg but again, bit rate is everything.