To get the client's signature directly in the web form, use the extra element "Signature". To add the "Signature" field to the form, you need to click on the selected field or drag it to the right, then you will see the added element on the right:
After you have added the "Signature" field, click on the "Edit" icon and a pop-up window for editing this field will open in front of you:
In the edit mode, set the field values in the "Width" and "Height" fields of the field. The value and description of other fields, you can see here "The main parameters of the elements".
To view an already configured form, click on the "View" icon and the form will open in a new tab in your browser:
The added fieldt after specifying the signature will look like this: