Yes you can import existing HTML into PK4Connect to use it as a template.

On the Campaigns tab, click the campaign name, add the recipients to the Campaign and click the PK4Connect Email Campaign button. Give the Email Blast a name and click the next button and click the arrow button in the Setup Email Template screen and select if you want to create your own template, use the saved template or the Starter templates and click the next button.

Click the import icon on the "Setup Email Content" screen and you see the option to paste the HTML data to the template, paste the HTML data on the screen and click the Import button. Enter the template name and click the next button to save the template.

Now the template is ready to use for the email blast.

Import HTML file