It is different than other Wordpress templates.
You have to edit the following file:
wp-content/themes/hueman/parts/single-heading.php
Add the following PHPcode to the bottom:
........
#if you have nvidia make sure you install the nvidia-cuda-toolkit so hardware acceleration can be used
wget http://ffmpeg.org/releases/ffmpeg-3.3.2.tar.bz2
tar -jxvf ffmpeg-3.3.2.tar.bz2
cd ffmpeg-3.3.2/
./configure --disable-yasm
install prefix /usr/local
source path ........