Navigate to the "Themes" page in your StreamAlive settings.

Click on "+ New Theme" and choose a theme similar to your desired template to use as a starting point.

Give your theme a unique name and start customizing the elements (background color, text color, accent colors, etc.). Once you're satisfied with your design, click "Save theme".

To apply a theme to your presentation, you can go to the presentation settings and select your desired theme from the dropdown menu in the presentation editor.