Flames are found in the "item.dat" file in a custom folder.

First, create (not buy) the flame via the Flame Forge, then open the "item.dat" file of the player you want to use. Find this line:

FLAME0 0; 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Manually edit all of the zeros to the values from the forge (in order).

I.E. the first zero after the semi-colon is "bodypart" value, second is "timestep" value, third is "damping" value, and so on.

Then you know, the usual save-it-then-/lp-the-player-ingame.

Hope that's (somewhat) clear.