As long as you have not yet added a signature field for the signer in question, all other fields remain grayed out and you cannot (yet) add them.
When you add a signature field for at least one signer, the other fields also become available to place on the document. This is because these fields are linked to a signature field. Without signature, no fields possible.
Do you have any questions about adding text fields? Please contact the ValidSign Support Team.
They can be reached via support@validsign.nl or 085 303 36 76.