I want to import Adobe XD Templates to Adobe Express to make sure that others could also use the same design with a easier software
You should ask the same question in the Adobe XD support forum.
In the meanwhile, I will assume that by an Adobe XD template you meant a stock image (or similar asset) that can be exported as an image file format suported in Adobe Express.
So, depending on the type of XD template, you can save it as a Creative Cloud file that can be shared among all of your Adobe apps.
Once you've uploaded and saved the desired template to your Creative Cloud Library, the Adobe Express app have access to that Library (or to any folder that you've created there).
It is easily accessed directly from your Adobe Express app through "Home" -->> tap on the "+" icon --->>> in the next screen, bottom margin, tap on the icon "Library".
You must be signed in with the Creative Cloud app to get to next step.
See more insightful features in the link below on how to share assets with the Creative Cloud app accross your favorite Adobe apps:
Let us know if this helps.
Specifically look at the tips in this additional guidance:
I sought additional guidance In the Adobe XD forum to clarify a few points.
See also this reply:
You're very welcome.