Before you import the asset from the asset store make sure you have already imported the DoTween asset and NodeCanvas. Then just as you would any other asset just import it and it will automatically create a folder called NodeCanvasAddons where it will add the DoTween actions, you do not need the examples if you already know how to use the functionality contained however that is up to you.
Once installed you will notice that when you create an action, you now have the DOTween sections in the drop down, as shown below.
You can then drop in any of these actions to use within NodeCanvas, there will be the same new sections for conditions which will allow you to check if tweens are playing etc.
Other useful links: