The best way I've found is to download Adobe Media Encoder, under that same trial period. Then in After Effects, use the send to Adobe Media Encoder menu command. In Media Encoder, you can pulldown the format to H264 and you'll see presets for many devices and uses (iphone, android tablet, youtube, etc.). These are mostly MP4 presets.
Hope that helps,
You need to use the Adobe Media Encoder to render. Please check the last video in this series: Basic Workflow
If you plan in working in video it is critical that you learn and understand video formats, frame rates and the standards that each must conform to.