Hi there,
Inside the Community Folder, where your MSFS Marketplace add-ons are installed, you should find a folder called pilots-aircraft-b314clipper, and inside that folder you will find a folder called Manuals.
The Manuals Folder contains a PDF document called PILOT'S_B-314_Seaports_Installation_Guide.pdf that details the procedure to install the B-314 seaports.
Cheers,
Jerome