How to add my own logo on the customer notification emails?

With Shopify, it's fast and easy to do!  

Go to the settings of your store and click on Notifications
On the next page, click Customize
Then, on the personalization page you can send your logo and change the dominant color of your emails.    
Be careful, this does not dispense you to add your logo inside the T-Pop app: the logo sent in the app will be used on packing slips.