The simplest method for transferring the figure into perspective is to make a drawing from life, or trace a photograph, that shows the figure in the correct pose and from the correct point of view to match its orientation in the master drawing. This figure study is then scaled to the appropriate size and traced into location.
perspective drawing using a viewing grid
the figure is copied square by square from the viewing grid to a smaller grid on the paper, and this drawing is then scaled to fit the master painting; from Dürer's Vier Bücher (1528)