You can change the Renew to Shadow Word: Pain at #showtooltip if you’d like that icon instead.
Here is an explanation if you’d like:
-Each line is a command, each command has to start with a / as shown by other things in wow i.e /say Meaning that even if you enter /cast Renew into your chat box it will work.
The text inside the brackets [ ] are conditionals that have a effect on whether the action of casting that spell is carried out, if what is inside those brackets is true then the spell is casted.
The bottom /cast [@player] Renew is the third case where you do not have your cursor over someone and you’d like to cast it on yourself, this is needed as placing your cursor over your character does not produce a tooltip.
The semicolons at the end just imply that command is over however you would like to use the same command but with what comes after the semicolon. Meaning this #showtooltip Renew
/cast [@mouseover,help,exists,nodead] Renew;[@mouseover, harm,exists,nodead] Shadow Word: Pain;[@player] Renew
is equal to what I originally gave you.
Make sure that you don’t have any return characters in your macro lines. If the game sees a new line that doesn’t start with some sort of command (such as /cast or #showtooltip) it dumps the text into chat. So, for your macro, the only place there should be a carriage return character is after the #showtooltip line.
Edit: Oh, and because sometimes I find carriage returns and other errors sneak in when I’m testing macros, I like to head to my Garrison for testign macros and make sure that /say is the last channel I’ve used. (Although any out of the way place can work.) Then when I mess up only I know!