When I work on my stuff in after effects, I want to see what I did in real time. So, I press the render button, or the 0 near the number pad.

But when I press it, it says that there is an error and I need at least 2 frames to render.

How do I change it so, its more that 2 frames?
When I zoom in, I see the green rendering line, and its only on the first frame, it never passes.