If you want to change your default black background color, a common way is to make a solid layer with preferred color then move it to the back.

Another, less common, way of doing this is to just change the background color. Hit Ctrl+Shift+B and you will get this window:
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In most other programs when you want to change the name of a layer, you just double click the name and start typing. This is not the case in After Effects. To change the name you need to first highlight the layer by clicking on the name. Then hit Enter (Windows) or Return (Mac OS). read more