I am a mac user. How do I get started?

OutSystems (via ServiceStudio) can only be used with Windows.

http://www.outsystems.com/home/document-download/1237/88/0/0
(Search for "Development Tools Requirements")

Use Paralells desktop

http://www.parallels.com/au/products/desktop/

Also follow this post to avoid DPI related issues:
http://www.outsystems.com/forums/discussion/11856/running-service-studio-on-non-standard-dpi-configuration/