I am trying to install Gifsicle on my server which is CentOS x86_64. I do not know which package to use or how to install it. Can someone with experience help me out?
If you don't want to download the source and compile it yourself, you should try to locate a RPM for your platform (e.g. from http://packages.sw.be/gifsicle/), and install it using
rpm -Uvh <filename>
I am way late to the party, but! An RPM for gifsicle 1.68 is available on repoforge [edit: link removed because StackOverflow privileges]. I was able to install this on CentOS 6.7.
Fedora maintains RPMs for the latest versions of gifsicle, but they don't appear to work for me on CentOS 6.7. The gifsicle 1.88 package requires GLIBC 2.14, and CentOS 6.7 (which I'm using) is stuck on 2.12. Folks on CentOS 7 might have better luck installing the package, though.
[Edit] EPEL now has a gifsicle 1.88 package for RHEL/Centos 6: https://dl.fedoraproject.org/pub/epel/6/x86_64/repoview/gifsicle.html