Hi,
There's no "enable" switch — SP Page Builder outputs Twitter Card tags by default. What you'll find instead is a switch to turn them off:
SP Page Builder → Settings → Options → Open Graph → Disable Twitter Card. Leave it off (that's the default). It sits inside the Open Graph group and is worded as a disable, which is why it didn't stand out when you looked under Settings → Options.
The card content comes from the per-page Open Graph fields you were already pointed to: frontend editor → Page Settings → SEO → Open Graph. The Open Graph Title becomes twitter:title and the Open Graph Image becomes twitter:image, so fill both in or the card renders bare.
To confirm it's working, open your page, view source and search for twitter:card.
One thing worth knowing: the card is output as twitter:card = summary — the small square thumbnail. There's no option for summary_large_image at the moment. If that's what you're after, let me know.
Tested on SP Page Builder 6.10.0 with Joomla 6. If the tags are missing on your site, let me know your SP Page Builder and Joomla versions and I'll check.
Best regards,