First use the level editor to create the custom levels you want to include in your map pack. Instructions for creating levels can be found here:
http://www.chroniclogic.com/pontifex2/pfx2manual/levels.html Download the map packer here:
http://www.chroniclogic.com/demo/packer.zipUnzip it into your Bridge Construction Set folder (normally c:\program files\Bridge Construction Set\
Run the file packer.exe.
Enter the name of the map pack you wish to create under NAME, for this example we will call our map pack "custompack"

Enter the name of each of the levels you want to add to the map pack under each LEVEL field. Do not enter the extension for the file name (.pfl), just enter the actual level name. So if your files were "custom01.pfl" and "custom02.pfl" you would just enter "custom01" and "custom02". Leave any extra lines blank:

If you would like to have ending text for when someone completes the map pack click on ENDING at the top of the window and then enter the text in as many lines as it takes on the ending screen:

If you would like to have a description for your map pack click on DESCRIPTION at the top of the window. Enter the description for your map pack on the lines below description:

When you are finished click SAVE in the bottom right corner of the window. This will create your map pack file which will be whatever you named it with a .pfm on the end. So if you named the map pack custompack the file will be custompack.pfm:

Now create a folder with the same name as your mappack (without the .pfm) so if your mappack name was "custompack" you would create a folder named "custompack" in the same folder as your custompack.pfm is located. Now copy all the level (.pfl) files that you added to your map pack into the folder you just created. Now your file structure is all ready for distribution. You can just zip up the mappack (.pfm) file along with the folder of the same name which contains all the level (.pfl) files:


To install the map pack just unzip or copy the map pack (.pfm) file and the folder with the same name which contains the level (.pfl) files into the following folder.
Windows:
"Bridge Construction Set\files\"
OSX
"Bridge Construction Set\bcs.app\Content\Resources\files\
Linux
"HOME\.Bridge Construction Set\Files"