Despite After Effects not being a video editing program, you can enhance your videos in After Effects. There are plenty of ways to practice enhancing your video in After Effects.
The first step is to import previously edited video into After Effects. You can import it with “file, import, file, select the video” or by taking a clip from Premiere, right clicking, hitting “make After Effects composition” (with After Effects already open), go back to After Effects, copy the video on the timeline, paste it on the composition timeline you were working on, and close the videos composition.
You can move the video on the timeline to where you want it to start. You can create a fade in by changing the opacity. You can control the videos volume here as well. You can add text on top the video by putting it above the video on the timeline. You can add effects or particles the same way.
You can change the length of the video on the timeline. Hover over the end of the video on the timeline until two horizontal arrows appear. Then you can drag it to make it shorter or longer. You can rename the layers to keep it organized, create composition folders within the timeline, and color code the layers.
Editing video in After Effects requires patience, time, and practice. Take some time to play with it and get comfortable using it. What creations would you make?