Existe um lugar para colar isso?
When in Outlook, press Alt+F11. That's where you can develop your macros/functions. You will probably have to modify your code before you run it though. An alternative to the hotkey is enabling the Developer tab and clicking 'Visual Basic'. You can read about that here.
Ele será executado automaticamente?
It depends on your implementation. I can think of three on the top of my head:
You can create a rule to run a script on specific actions.
You can run it on a schedule
Since you are using Outlook 2013 you may need to modify the registry to allow scripts to be run from a rule.
Eu teria que colar isso em todos os convites que eu criar
Nope. When a macro is created, it stays created even when you close out of Outlook (unless you don't save it!!).