What you need:

1. Your branded template for your Canva. Depending on what you have chosen, you might have a blank frame in the transparent background (see figur 1) that you can superimpose on your product images, or a blank template where you can add your own quotation on the Instagram.
2. An account for Canva. You can set up the free account on www.canva.com 

Once you set up your Canva, follow this instructions on this short video:  

VOILA! It is that easy! If you need more help or tutorials, head over to https://www.canva.com/learn/design/tutorials/.