On a cpanel web hosting server, to install ImageMagick you need to run if you got it running or not
# /scripts/checkimagemagick
If you installed Imagemagick via the rpm package
you can find if it is on your system or not by :
rpm -qa |grep image
If all the answers are no, you can simply install it by running
# /scripts/installimagemagick
To hook PHP to ImageMagick, you need to also install it via WHM
Log into WHM >> Software >> Module Installers >> PHP Pecl and install imagick to get the whole thing binding into PHP