There are several steps to follow:

First of all, the data from your source, in this case the GSheet document, must be published.

Otherwise, they are not accessible and therefore impossible to exploit them in a third party tool.

How do I publish a Google Sheet document?

File > Publish to the Web

click on Publish

From there you can retrieve the url of your document directly in the browser

Then, you can retrieve the id of your document which will be asked when creating the connector, it is highlighted in blue in the image above.

From the connector tool, click on Add Connector

In the list of templates, choose the Google SpreadSheet connector

All that remains is to configure the fields retrieved from the source.

Fields => this corresponds to the column headers in your file. These cells are therefore not editable.

Name => Here you can rename these parameters as you wish. This is what will be displayed in your report.

Type => Is it a metric, a dimension, a date?

Aggregation => Here you configure the format and aggregation. It all depends on the data.