You can access, add and configure these technical configurations to your menus in following way.
Navigate to this option by going to your website admin, browse to Appearance > Customize > Menus > Select a Menu.
Click on the gear icon at the top right of the Menus tab, and right below the question icon. It would expand the tab to showcase a list of options with the following contents
- Link Target
- Title Attribute
- CSS Classes
- Link Relationship (XFN)
You can click on the checkbox right next to any of these to enable the option for the menus.