Interface
You don't really need any insane UI to play the game, but you should download addons like Skada, bigwigs and maybe Weakauras to help you keep track of what's going on around you.
Macros
Marcos are very simple for Retribution Paladin, it's really just mouseover.
Flash of Light Macro
#showtooltip flash of light
/cast [@mouseover,exists,help] Flash of Light [@player] Flash of Light
Lay on Hands Macro
#showtooltip Lay on Hands
/cast [@mouseover,exists,help] Lay on Hands [@player] Lay on Hands
Blessing of Protection Macro
#showtooltip Blessing of Protection
/cast [@mouseover,exists,help] Blessing of Protection [@player] Blessing of Protection
Blessing of Freedom Macro
#showtooltip Blessing of Freedom
/stopcasting
/cast [@mouseover] Blessing of Freedom
Cleanse Toxins Macro
#showtooltip Cleanse Toxins
/cast [@mouseover] Cleanse Toxins
PvP Blessing of Sanctuary Macro
#showtooltip Blessing of Sanctuary
/stopcasting
/cast [@mouseover] Blessing of Sanctuary