Tap the camera button to open the camera and then tap the spirograph-star button in the lower-left corner. To get to the new photo filters, open the Messages app and start or reply to a conversation. But you can easily create a comic book photo of yourself and either text it or save it to your camera roll.
Why Apple hasn't added them to the Vivid and Dramatic filters in the Photos app? No idea.
Like Memoji, you'll find the new photo filters in the Messages app. Where to find iOS 12's comic book photo filters
