macro a spell and key binding

I know there is tons on information on macros but I cant seem to find the answer, and I am very new to this. ( have read making a macro on wowpedia like 10 time to try to learn this stuff)
learning to 2-5 boxing
Rogue -starting level
I set up IWT in ISboxer with hot key( alt J for now cause that's what the video had) and set in wow and this works
What I want to try is to have the #1 key (interact with target - Alt J) and use my Sinister Strike
If anyone can help with this and link more guides and vid's that would be great. I have like 25 links and am watching 10-12 vid's a day. but I want to play as well so trying to balance palying and learning. thanks, you guys rock, I love this!

[MiRai]

You'll want to point a Do Mapped Key Action at your IWT Mapped Key with a Target of Window:Current.

So then is this possible to add assist to my dps(ranged) just like the green overlay broadcast in quick setup? or this not a good idea in the long run. I can get it to work once but when my tank switches target dps9ranged) stops.
Fixed
I finally pulled my head out. I needed assist on tank so ranged dps would target the correct mob. now is this something I might not want to do with later progression. eg more spell differn't rotation?

[MiRai]

now is this something I might not want to do with later progression. eg more spell differn't rotation?

It's pretty much up to you on whether you want to use a built-in auto-assist or not. I prefer a separate, manual assist myself because I feel it gives me more control.