#show
/cast [harm] Attack Spell; [help] Heal Spell

This will show the icon on the spell you're about to cast.
The same button will cast a harmful spell on a hostile opponent, for example Lightning Bolt.
It will cast a healing spell on a friendly target, for example Lesser Healing Wave.
Just plug in the spell names.

I'm not sure the equivalent of [help] and [harm] in your language, but whatever wow uses you'll need the right terminology.
Then just plug in the desired spell names.

I mix them like this:
Lighting Bolt / Lesser Healing Wave
Chain Lighting / Chain Healing

Down the road, 74th I believe, you'll have Lava Burst which does a lot more if Flame Shock is on the target already.
For my other offensive spell, I use:

#show
/cast [mod:alt] Flame Shock
/castsequence [nomod] reset=10 Flame Shock, Lava Burst, Lava Burst

This will cast Flame Shock, then Lava Burst, then Lava Burst (resetting to Flame Shock after two Lava Bursts or if you don't press the macro for 10 seconds)
If you wish to Flame Shock immediately, press it with Alt held as well.