Do you mean the Apache that ships with OS X?
If you want to enable it go to System Preferences / Sharing and select Personal Web Sharing and bingo you turned on the Apache system.
If you want to enable php etc you will need to log in as the root User (disabled on OS X) you can enable root using the Terminal shell utility, or the net info manager utility (both found in the Utilities folder within the Applications folder). To use Net Info Manager, select security/authenticate then enter your password. Then select security/enable root set the passwords etc and there you have it. Now log off log back in and you can addminister your appache files as standard, removeing #'s etc to enable the php module (it's already instaled by default). Couldn't be easier
It's all very easy to pick up and there's lots of handy little Utilities etc to help you out, if you get to concerned you can always hit the Terminal...
Hmm, I don't know what flatyper is.