Hey @email@example.com! It sounds like you might be using our Text Only template, which is admittedly quite plain in terms of styling.
I'd recommend creating a new template and adding whatever styling you'd like. We have a guide on our visual template editor here: The Visual Email Template Editor226
Once your new template is created, you can select it as your default from the templates page in your account (linked above), by clicking the 'Use this template' button that will show up underneath it.
I hope that helps! 🙂