Hey Derrick, you can create a form in Marketo and set the Twitter lead generation card to post to your form. You don't need to add any fields to your form, they will be managed from Twitter. From there you can customize the 3 user information fields (name, email, and Twitter screen name) and pass the other hidden fields needed. Since the Twitter name is just one string for the full name (or whatever the user will type there), I highly recommend to post it to a custom field and not to your First Name field.
Here is the complete procedure:
https://launchpoint.marketo.com/assets/Uploads/Twitter-Card-Integration2.pdf