you need to update the CSS styles in your Odoo theme. Here's how you can do it:

1. Identify the CSS class or selector that applies the font style to the website elements. This can vary depending on the specific theme and template you are using. Look for classes like body, h1, h2, p, or any other element selectors that define the font style.

2. Locate the CSS file where the font styles are defined. This can be in your custom theme or in the Odoo default theme. You can use your browser's developer tools to inspect the HTML elements and find the associated CSS file.

3. Open the CSS file and search for occurrences of font-family: 'Roboto', sans-serif;. Replace 'Roboto' with 'Poppins', sans-serif;.

4. Save the CSS file with the updated font styles.

5. If you are using a custom theme, make sure to upload the modified CSS file to your theme's assets folder.

6. If you are using the Odoo default theme, you can create a custom theme module to override the CSS file. Place the modified CSS file in the static/src/css directory of your custom theme module.

7. Restart your Odoo server and clear your browser's cache.