The chord runs from the trailing edge to the leading edge. The trailing edge point is usually pretty easy to identify. The leading edge point is a bit tougher. Various geometric methods could be used. Take a compass and put one point on the TE point. Adjust to where it is wide enough to only barely touch the leading edge. mark that point - draw your chord. You could also find it by finding the point where the line tangent to the leading edge is at a right angle to the line from the tangent point to the trailiing edge.