Here is a sample code
I hate putting comments in code so try to understand it.
[X,Y,Z] = peaks;
contour(X,Y,Z,20)
hold on
xl = xlim;yl = ylim;
no_of_points_x = 5;
no_of_points_y = 5;
locX = reshape(repmat(linspace(xl(1),xl(2),no_of_points_x),no_of_points_y,1).',no_of_points_x*no_of_points_y,[]);
locY = reshape(repmat(linspace(yl(1),yl(2),no_of_points_y),no_of_points_x,1),no_of_points_x*no_of_points_y,[]);
plot(locX,locY,'.','MarkerSize',80,'MarkerFaceColor',[0 0.4470 0.4470])
text(locX,locY,strcat('P',string(1:no_of_points_x*no_of_points_y)),'HorizontalAlignment','center','Color','y')
set(gca,'YDir','reverse')
