Ahh, you've just added the CSPROJ files. What you need to do is open the Farseer Physics Monogame solution, copy the source folders and class files as-is into the new project, it should look like this:
Obviously, the folders should contain the same structure and content as the Farseer Physics Monogame solution, but only the classes and folders, not the rest of the stuff.
Also, seems like your Monogame for iOS reference is wrong, you might need to delete the reference and re-add it (or re-add the NuGet package).
Give it a go and let me know if you get stuck.