Don’t you have the Custom Heading WPBakery element in the list of the WPBakery elements on the page? On your screenshot you use simple Text element but Rose suggested you to use Custom Heading element.
Also, you can switch to HTML tab instead of the visual and add the style tag for your paragraph, for example <p style="font-size: 14px;"><Puedes lavarlo junto al resto de la ropa, pero si lo haces en agua fría y sin suavizante, mejor.</p>
Or add the below custom code to Theme Options > Custom CSS to change the size of the paragraphs on the whole site
p, .tabs .tab-content p {
font-size: 14px;
line-height: 1.4;
}
