How to install maps?

I downloaded a single map, and I'm wondering where to put it. I've heard people talk about this profiles folder, but I have no clue where it is. By the way, the extension of the file is .PFB.

[Chronic Logic - Josiah]

Here are the default locations of the profile folder.  It will only show up after you have started the game.  Save any .pfb files into your profile folder to load them.  If they are .pfl files they need to be saved in the levels folder.

Windows:
c:\program files\bridge construction set\profile\

OSX:
The profile folder is located inside the bcs.app, you need to cmd click on the bcs.app and select "show package contents". Then navigate to the "Content/Resources" folder.

Linux:
The profile folder will be located in your HOME directory inside the ".Bridge Construction Set" directory.  Please note it is hidden and wont show up with a normal "ls" command.