First Steps > View Localhost
Your default host for MAMP PRO is “localhost”. The files for localhost are initially located in the “~/Sites/localhost” folder. Press “Open” located to the right of the “Name” text box to open up the localhost in a web browser.
Note: It is no longer recommended to use "/Applications/MAMP/htdocs" as "Document root" for the host "localhost" (or any other host).