How t define fields in a multi document envelope

Hi,

I have an envelope with seven different documents both Excel and Word.
They need to be signed from a supplier and our management.

When creating the envelope, I didn’t see buttons/ options to set and define the signature fields.

Strangely, before submitting the envelope for signature, DocuSign system asks me if I don’t prefer adding fields.

My question is: HOW?

Thank you for your help!