I am new to Archi and ArchiMate is this tool / methodology useful for documenting existing enterprise architecture? Where can I start?
Hi,
Well, ArchiMate has been created to document your Enterprise Architecture (your current one, your future state and the way to move on that road) ;-)
The best way to start is to read Gerben's book "Mastering Archimate (http://masteringarchimate.com/mastering-archimate-edition-ii/)". If you're really new to this read first the Excerpt version (which is free), but I really recommand buying the full book as it contains plenty of real life examples.
Regards
JB