Let's import a large image (at least 1920 x 1080) by double-clicking the open area. This brings up your media folders. You can click anywhere in the area where I'm standing in the image below:
- Drag and move this image into the images folder.
- You can rename your images by right clicking on the layer.
After Effect that references material; it doesn't actually keep anything in the project it references things. You never want to rename a file outside of After Effects. When you import images into a Photoshop document it saves a copy with the document. However After Effects links to the assets you import into your project. You always want to leave the name unchanged because After Effects will not be able to find the new name for its referencing and you will get an error message.
Rather than renaming or removing your files from After Effects, it's better to create a copy or not move it. If you need to replace a file you have to right-click on the layer and choose to replace or reload the footage:
Practice renaming and relinking your files a couple times just to make sure you understand that concept.
If you need to delete anything drag it to the trashcan highlighted in the following image:
