Open up your macro interface (either hit escape and click on "Macros" or type /macro
Click New - type in a name for the macro and select an icon for it
Copy-paste the macro into the code box, drag the macro (from the top section of the window) to your bars
Note: you can have the macro show your information for Righteous Defense by selecting the ? icon and by putting this into the first line of the code above the /cast part:
Code:
#showtooltip Righteous Defense
So then, the whole macro would look like this (on 2 lines):
Code:
#showtooltip Righteous Defense
/cast [help,nodead][target=targettarget,help,nodead] Righteous Defense
That way, you'll have the Righteous Defense tooltip instead of a macro tooltip that just says the name of your macro.