Are you the Sender of the envelope? The question posed is very broad and I do not know if you are the Sender of the envelope or a signer or you may have just received a signed document in your email that you need to send to more individuals. So I provided a few general scenarios.

1) If you are the Sender, you can "Correct" an envelope and add new Recipients, if the envelope hasnt been completed.

2) If you need additional signatures to a document, you could send through DocuSign either by using the Send an Envelope or if the envelope was something you were part of and needs an additional signature forgotten in the original Send then you could use the Forward option.

3) If you are just a Signer to the document and you need to involve other individuals to sign, BUT you are not the Sender nor were you set as Specify Recipients or Update Recipients, then you would need to contact the envelope Sender to have more Recipients added.

4) If you were set as a Recipient, but someone else needs to sign instead of you, there should be an option to "Assign to Someone Else".