Your existing project needs to have a .vue-translation.js config file prior to using vue-translation-manager from the CLI.

This file contains configuration for the translation manager and the setup of a suiting adapter and could look like this:

const path = require('path')
const { JSONAdapter } = require('vue-translation-manager')

module.exports = {
  srcPath: path.join(__dirname, 'src/'),
  adapter: new JSONAdapter({ path: path.join(__dirname, 'src/i18n/messages.json')}),
  languages: ['en', 'de']
}

In this case we're using the provided JSONAdapter and we're saying that all our translations will be stored in a file called messages.json. For configuration of the JSONAdapter see the documentation on it.

As soon as you have this configured, you're good to go.