I have bought Magento template. It has product comparsion disabled. I managed to display it on shopping cart page, but for some reason it is not visible in product category page (just select any category and it is that page). How can I display product comparsion in product category page ?
If it is missing then it is either:
removed : you can add this back to your template by comparing your theme template against the same template in app/design/frontend/base/default/template/ code with diff tool suitable to you (winmerge.org under windows, changes under os-x and so on)
not working: start to debug the variables and conditions and again compare to initial implementation in base directory template (refer to point 1.)
Ps: even tho you are not Chuck Norris and you don't have the Magento manual then you can always use the common sense and basic theming guides/understanding to compare changes against defaults. It's the same in every project/software/woodwork and so on. Your biggest improvement on getting magento documentation would be understanding the concepts and using version control (to be able to travel back in time), diff (tools that give you understanding about differences) and grep/awk (to ease your way through codebase)