Step 1 Add your MP4 files. Begin with and running the UniConverter then click the Downloader tab. Next, go to YouTube, search for your video, then paste then copy the video link. Now return to UniConverter and tap the Paste URL icon. Step 2 Download MP4. From the pop-up window, select whether you want to download the file in either MP4 or MP3 format. If you want to convert it to a different format