No problem, it’s not that difficult. Magento
2.0

  1. Go to your Magento 2 admin.
  2. Go to STORES > Configuration > Design > Header
  3. Click Choose file and select your logo
  4. Click Save Config

Magento has changed this setting again from Magento
2.1 up

  1. Go to your Magento 2 admin.
  2. On the left go to Content > Configuration
  3. Click on “Edit” next to your theme
  4. Go to the Header tab
  5. Upload your logo image

As you can see it is much easier than in Magento 1.