Don't hit the space bar. Use the zero key on the numeric keypad.
And if you're new, please understand that trying to use AE intuitively only makes your life harder. For success in AE, you need a thorough grounding in the basics. This is an excellent place to start.
From your very brief description, I can't tell what exactly you're experiencing. Please give more details about exactly what you're doing and experiencing.
Also, be sure to answer the questions listed here: