In the "Survey Designs" Web Part, click at "Create Survey Design".
To select a Web Part, enter into "Admin Mode" by selecting " --> Page Admin Mode". More details in the FAQ How to change the contents of a page?
In the "Schema" dropdown box, choose "lists".
In the "Query" dropdown box, choose the table where to store the survey data.
Give a name and a description.
Click the "Generate Survey Questions" button. That will generate a survey based on the field names of the chosen survey table.
Adapt the proposed survey design as required. Some JSON code snippets can be extracted from the "Question Metadata Examples".
Add a "Surveys" web part with the previously created survey design "Test design". If necessary, check the FAQ How to change the contents of a page? to see how to add a web part.
Click on the button "Create Survey" of the "Surveys" web part to start to populate a new survey instance.