First, be sure to choose the Platform "Google Display & Video 360" in NEXD Campaign Manager.

Second, select and export the creative(s) as usual. You have two options:
you can download one Excel file with all the tags and creative(s') settings
- or -manually copy and paste all the tags and their sizes
When you have decided, click on:
"Download as Excel for Google Display & Video 360" button
- or -"View tag" link or "Download tag" icon
The next steps are in Google Display & Video 360 platform.
Create manually
As a full walkthrough:

And the same in simple four steps.
Step 1: Click "New", then "Third-party" and "Third Party tag".

Step 2: Insert the data and tag
Then, to fill the form:
Name - Name of the banner
Dimensions - the width and height of the ad in pixels
Landing page URL - the link to your desired click-out destination
Require HTML5 - check the field
Third-party tag - paste here the NEXD Campaign Manager Tag

Step 3: Click "Test tag" and check the preview so the creative is working.

Step 4: Click "Save" and you have your awesome ad in Display & Video 360.
Hopefully, it was as easy as it should be.