Basic After effects is waaaay easier than it looks.

Ok so on the far left you have your project library. Drag and drop the things you will be using for your project such as video files, logos, audio files etc.
Then select the video from your library for example and drag it in the timeline at the bottom right of the screen. The timeline is the area in the pic with the long horizontal stripes. Layer the elements in the timeline. So if you want a logo over the video it has to be above it in the timeline etc.
Also if you add an audio file and a video file it will mix the audio together when you export the video. This is what you want but to change the audio levels click on either the video audio track or your recorded audio vocals track in the timeline and go to the “windows” tab at the top of the program and enable the “audio” panel. With the audio panel you can adjust the audio level of any audio track you select in the timeline.
When your done playing around with all that then go to “composition > add to render queue” and in the render queue set the settings. I will send some later but it depends on if you want to export sd or hd. Try the presets.
Thats the basics but if you play with it you can pick it up easy. hopefully lol