As per the magento documentation guide logo can be uploaded from the backend in the Header section. See reference link.
But I am totally sucked with my magento 2.1 backend that there is no such section.
From Magento 2.1 admin structure are changed,
All Design configuration are moved to
Content -> Design -> Configuration section
You have to go for Admin:
Content -> Design -> Configuration
Now go to your current theme,
Click on current theme you have to display new page opened, Inside This page, You have to go for Header section at below of page,
Inside Header you can add your
Logo Image section.
Magento 2 allows us to change logo appearing in website header, transactional emails and invoice easily. In this tutorial, we will show you how to change the logo for all of these positions. The reason why we can’t use the same logo for all places is that the sizes of the logo for each of them are varied.
In this guide, we have shown you how to change your logo in Magento 2 at ease within 5 minutes.