Profile for presidentmesser

I am trying to go see Patti LuPone for the fist time in a couple months and I've never been to New York or a concert or anything before... so I have a couple questions. Firstly I read somewhere that if you write ahead of time you might be able to go backstage and meet her, does anyone have anymore information on this? Also I've never stagedoored before and I was wondering where do I keep a windowcard that I want her to sign? (I have the Sweeney revival one with her and Micahel) Do I h