Sure, I'd be happy to help you customize your Spotify playlist covers. Here's a step-by-step guide:

1. Open the Spotify app on your desktop. Unfortunately, you can't change playlist covers through the mobile app.

2. Go to the playlist you want to customize.

3. Hover your cursor over the playlist cover and click on the pencil icon that appears. This will open the "Edit Playlist" window.

4. In the "Edit Playlist" window, you'll see a small square next to the playlist name. This is where the current playlist cover is displayed.

5. Click on the square. This will open a file browser where you can select the image you want to use as the new cover. Please note that the image must be a .jpeg file and no larger than 4MB.

6. After selecting the image, click on "Open". The image will be uploaded and set as the new playlist cover.

7. Click on "Save" to confirm the changes.

8. Your playlist cover is now customized!

Remember, the image you choose should not violate Spotify's content policies.