Importing an existing Electron app into the Electron Forge workflow is very straightforward:
cd my-appyarn add --dev @electron-forge/cliyarn electron-forge import
cd my-appnpm install --save-dev @electron-forge/clinpx electron-forge import
cd my-appnpm install --save-dev @electron-forge/clinpm exec [email protected]/cli -c "electron-forge import"
If you're already using other Electron tooling (including migrating from Electron Forge v5), it will try to automatically migrate the settings as much as possible, but some of it may need to be migrated manually.