If you have already installed Magento 2 Blog Module v2.6.2 (or later) you can easily add a blog and blog categories links to the SmartWave Mega Menu.

Please, follow the steps listed below.

1. Log into your Magento 2 admin panel.
2. Go to the Content > Blocks.
3. Find a block with the identifier "porto_custom_menu" and open its edit page.
4. Add this code to the block content:

5. Save the changes & flush Magento cache.
6. Check :-)

You can also use another menu_type values (staticwidth, fullwidth) to change a look of the blog submenu items.