For testing data, the Element User ID is not available in the contact information view. This can be exported from a segment or it can be pulled from the URL.
The user ID below is 620e9b3534e7f364a5726292

The template GUID can be built from template URL. The pattern is “ending”.template.”template id”. The “ending” may be the client name or it may be something like “all” for prebuilt templates. Double check the URL when creating the template GUID.
For example, the template GUID for the image below would be “client.template.8071”.

Feature is not an authorization token. It needs to go in the header. For example, when using Postman, it should look like the image below.

When sending data for import, it would be in rows where the column is either the slug or a number and is offset by -1. For example:
Element Layout

Data Layout
{
"0": "12ab34cd56ef",
"1": "Tommy",
"2": "Testerson",
}