[Freesurfer] MEG data and ASCII format

Hello, I am trying to display MEG source location data on the surface. Does anybody have detailed information on this? I am looking at page 125 of the FreeSurfer manual and it describes converting from ASCII format to Curvature files, but I have a few questions. Right now, I have the MEG source waveforms and a program to compute the contours of activation through an inverse technique. Is there a specific format of the output for the MEG data? And when I make the ASCII file, what is the starting latency and the vertex index. I have the value and (x,y) coordinates for that value. Is the vertex index related to the coordinates? Thanks, any help is appreciated.

Sarah Rugheimer