First make sure ffmpeg is installed

If it is not installed type and follow the prompts

sudo apt-get install ffmpeg

Once ffmpeg is installed you can run the following command on your video file.

ffmpeg -i "INPUT_FILE.wmv" -sameq -acodec libmp3lame -ar 22050 -ab 96000 -deinterlace -nr 500 -s 518x288 -aspect 16:9 -r 20 -g 500 -me_range 20 -b 270k -deinterlace -f flv -y "OUTPUT_FILE.flv"