Update: here is another alternative solution how to edit Nikon D810 NEF/RAW files with Capture NX2 (with the free RAW2NEF software).
With the announcement of the new Capture NX-D, Nikon stopped supporting the previous Capture NX2 version, which means that you will not be able to use the software if you have one of the newest Nikon cameras. Peter Wijn has an alternative solution on how to use Capture NX with newer cameras like the D810: