Digital signature field doesn't appear on the form when sent via Send for signature

OK,

So I've created a form that I want to send to clients.

What I want is for them to fill in the info and then digitally sign the doc at the bottom.

In the form, I have selected the 'Prepare form' button on the right side.

Then from here selected 'Add a signature field' and added to the doc.

Now when I use the 'send for signature' option.

The client receives the email and has a redirect to the abobe page and when selecting the signature option they have 4 options: Type / Draw / Image / Mobile

They then choose to sign the doc via one of these methods.

However this is not what I want... I want the doc to be sent and the signature option to be 'Digital ID' only.

I've had this before from corporations, so I know it can be done. The question is I can't see how you edit the signature field to be digital ID only.

Help anyone? As all the documentation I can find regarding Digital ID is for setting up a signature if you've received a document requesting a digital ID - and not for creating a document with a digital ID field.

much appreciated

Thanks

Tony