Woocommerce Follow-up Emails (subscribe checkbox)

I recently purchase Woocommerce Follow up Email extension for Wordpress: http://ift.tt/1RPy0uf http://ift.tt/1Vnnpu5

It has a subscribe to email listing by manually entering an email.

I would like to write some PHP code to just have a box to tick for signup instead.

When a customer has logged in, on their member's area is the following checkbox:

<input name="email_signup" title="Email Newsletter" type="checkbox" checked="checked" value="Tick for occasional email updates.">

Any ideas how I can link this into the plugin?