How can I plot a dot on a framebuffer object?

I researched on the web, but I couldn't find a specific tutorial or example.

What I want to do is this: 1) Create a FBO of size screen_width * screen_height. 2) Plot 500 pixels/dots on it. Like a function called plot(x,y,red,green,blue) 3) Copy or draw the FBO to the screen

Can a simple example be provided? Thank you in advanced.