Hmm, it seems that AE might be a little bit too advance for you since you do not know even the most basic of things, but hey, people always have a first time.
I suggest you watch a lot of YouTube tutorials to get you started. Even Google searching wouldn't hurt, since those 2 options are much better than asking people here.
YouTube tutorials are the main thing. EVERYTHING I learn and know all comes from video tutorials.
First off, learn how to create a composition and how to render a video. AE's default video settings render out HUGE massive filesizes for VERY simple videos, and to fix that, download the Xvid Codec. Find your way on how to have AE render using the Xvid Codec by using Google or YouTube. Trust me, you would want to use the codec otherwise it's better off just not using AE since the file sizes are huge (without codec: 5sec typography vid = 5-7GB, with codec 5sec = 3mb).
Learn how to render a video, and configure the settings, all through YouTube.
Mind if I ask what are you using AE for? AE is very advanced and are for visual effects, compositing, motion graphics and all that. It's not necessarily for "video editing" (cutting videos, adding text/transitions/titles) if that's what you might be into. Otherwise I welcome you to the world of motion graphics and video effects
