This has been probably been answered before .........  After entering info onto  FMC pages "V-speed not available" appears . What have I entered incorrectly??

Runway length not appropriate for takeoff. Based on the aircraft configuration. (I think)

What have I entered incorrectly??

FCOM2, page 11.60.7 to 8 - FMC Entry Error Messages.

and please,  where does one get the above referenced ??

It should have been installed with your PMDG 777. 

and please,  where does one get the above referenced ??

Microsoft Flight Simulator X/PMDG/PMDG 777X/Flight Manuals

 

 

After entering info onto FMC pages "V-speed not available" appears . What have I entered incorrectly??

 

Most likely  you havnt  entered  your departure  rwy etc or  your  alt or  you havnt  executed your info make sure yo have entered  all info

I got this a few times before, although it was on the 737. But the same principle applies. For me it was a case of forgetting to hit the execute button on the FMC.

I had this problem over the weekend. Turned out that in a fit of slapdashery I hadn't entered appropriate fuel or ZFW figures in FS Actions. So it saw a discrepancy bewtween the imported perf figures and the unaltered fuel/ZFW figures. So lesson learned and worth doing things properly as you're supposed to. So you could add that to the list of already mentioned items as possible causes.