You can do a Twitter export in two different ways. This first way is to choose the Audience you want to export while you are in the Audience tab. Click the "Take Action" button next to your Audience.
Then, click the export icon in the modal.
Next, name your export and select "Twitter" as the template from the drop down under the .CSV tab.
The next screen will pre populate the necessary information to import data to Twitter for advertising campaigns. You can select any additional data you would like to add in the export. Click "Configure Export" to complete the export. The export CSV will include a Twitter ID as well as an email address. You can use either of these to import into Twitter to build an audience or an ad campaign.
The second way of doing a Twitter export is to go Toolkit > Export > Create New.
Then, select your audience, name your export, and select "Twitter" as the template from the drop down under the .CSV tab.
Click "Configure Export" to proceed with your export.