1. Access the {% data variables.product.prodname_vscode_command_palette %} (Shift+Command+P / Ctrl+Shift+P), then start typing "add dev". Click **Codespaces: Add Dev Container Configuration Files**. ![Screenshot of the Command Palette, with "add dev" entered and "Codespaces: Add Dev Container Configuration Files" listed.](/assets/images/help/codespaces/add-prebuilt-container-command.png) 1. Click **Create a new configuration**. 1. In this example, the template repository from which you created the codespace already contains a dev container configuration, so a message is displayed telling you that the configuration file already exists. We're going to overwrite the existing configuration file, so click **Continue**. 1. Click **Show All Definitions**. ![Screenshot of the "Add Dev Container Configuration Files" dropdown, showing various options, including "Show All Definitions."](/assets/images/help/codespaces/show-all-definitions.png)