Your Subscription Preferences question will probably look something like this:
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The labels on those checkboxes are the Friendly names of the groups they represent, so the first thing you'll do is set up your groups and give them friendly names.

NOTE: You'll probably want these groups to be Public, so they're visible on your Unsubscribe page. That way, a contact can opt out of these specific groups/mailings, and not all of your emails.
Your additional options may include:
or any other special mailings that your subscribers may opt in to!
Once your new groups are set up, you're ready to add your "Add to Group" Field to your sign-up form. Select Add to Group from the dropdown menu:

Update your Field label as you like, for example: "What kind of mail do you want to receive?" Then, select the groups that you just created as your checkbox options:

That's it! Preview your form to see how the friendly names appear in the field:

If you have specific questions on how to customize your email sign-up form, please reach out to your account representative!