Normally, when using MAMP ( I am presently using the FREE version of MAMP) you view the site you are working on in a couple of ways.
Put your web site in the /Applications/MAMP/htdocs/ folder and point your browser to http://locahost:8888/
or (This is what I like to do for multiple site management)
Put your sites in appropriately named folders under the “Sites” folder.
Click on MAMP Preferences and select the “Apache” tab. Then click the “Select” button and browse to the “Sites” folder.
That way, you can easily get to any of the folders by typing in the URL http://localhost:8888/. You will be presented with a list of folders (as links). These folders are the sites you are developing under the Sites directory. Just click the folder (link) you wish to view and you’re there.
Hope this helps!