By default they don’t have a fly.toml and if you generate one, they don’t have an image or build.
The image bit could certainly be better. To make this work, you will need to download the configuration file by running fly config save --app <app-name> and make your changes. To apply the changes, you will need to deploy while specifying the --image argument.
Note: Be sure to be mindful of the directory you’re in when you download the configuration file.
fly deploy . --image <repository>:<tag>
To determine what image you’re currently running, you can run the following:
fly image show
Let me know if you have any other questions!