Hello,
You may not be able to do this with these limited set of values. If you want to place marker on the place of your click, you need to define the plot with more points. To explain this, please take a look at this code below.
x = (1:0.001:10); %defining a large number of points instead of 10
y = sin(x); % a continuous function
plot(x,y,'-o');
Hope it helps