Collecting Help for Austria

[Historicus]

Hi there!

Sorry to be a bother but waht is the right amount of Postage, Envelopes, etc.... for writing, f.e. Neil Patrick harris for an autograph from Austria?
I live at Vienna, the capital of Austria.
Would anyone please give me some sort of plan how to do so?
Like:
1. This envelope
2. this amount of postage
3......
4...
etc.?

if this topic has been up already, I'm sorry, i just haven't had the time to read through the posts here at work.

Kind regards
Alex Winkler