When using email templates, how do you change the "to: " field?

When using email templates, how do you change the "to: " field?

Hi,

I've created an email template called "Blah", which fits under the 'Contacts' module.

When I go to the Accounts tab, and click on the account "Green", I scroll down and "+ Send Email"

A new email pops up, and I open the the template "Blah".

The template has the "to: " field populated as the email address on the account.

How do I change it such that when I open the template "Blah", it populates a different email address " internal@company.com"?

Thanks
Matthew