Step 1: Run HandBrake after you install it on your PC.
How to convert FLV to MP4 free with HandBrake? This open-source tool also allows you to add subtitles, modify presets, trim/cut/crop videos, and even rip DVDs. It can help you convert from nearly any format to a selection of common formats and codecs, including FLV to MP4. HandBrake is a popular converting tool for Windows and other operating systems.