If you want to upload your own generated map from your PC then you can do so by doing the following:
- Generate the world on your PC
- Open up File Manager and click on 'Worlds'
- Click 'Upload'
- Navigate to Documents\My Games\Terraria\Worlds
- Upload your world
- Open up configuration files
- Click 'Configuration Editor'
- Tick Load Existing World
- On the drop down select your world
