What have you done?!!! OK after you root its not necessary for you wipe your data or system! ROM manager is a necessary tool although its a good tool for peopl who flash their phones very often
I suggest you to head over to the galaxy s4 sub forums and find a suitable ROM for you , the install instructions are mostly the same for all ROMs, but some ROMs have specific ways to install, details about which will be provided in the ROMs thread.
Please hit thanks if I helped you! It doesn't cost a single penny you see!
May the force be with you!