Download Handbrake (Free opensource Video Compressor)
Go to Final cut.
Export your video uncompressed. (Masterfile)
Import video into Handbrake. (Source)
Choose mp4, H264, videosize, constant framerate etc.
Check web optimized.
Check 2 pass render.
Adjust the bitrate at 5000 kbps for 1280x720 video or 8000 kbps for 1920x1080 video.
Click on preset (top right) and then on the + sign to save the setting.
Click on the Play button to launch the compression.
And you are set.