It's probably already installed. Open a shell on your server and type convert. If it spits out a list of commands you're good to go, if not then type
yum install ImageMagick. That will install it.
You're best bet is to ask godaddy to help you or find someone who knows how to admin a server. You don't want to be playing around in there unless you know what you are doing.
The only way you can install Imagemagick is if you are running a VPS/dedicated server. If you are on a shared host, then you have to either hope that they have it installed on that shared box or request them (your hosting provider) to install it, and then it is installed for everyone.
Pretty sure that GoDaddy has it https://www.godaddy.com/help/how-can-i-use-imagemagick-on-my-web-site-209
The PECL for it needs to be enabled also for the PHP processor.
ImageMagick isn't difficult to install at the command line, using yum or apt, but one needs to be cautious about the version a respective linux distro will install. Many distros install an older version.