I am not completely clear on the overall issue, it sounds like you are asking how do I create an envelope that I sign and that goes to another Recipient to sign on the same document? Is that accurate?

yes that is the question.

When you create a new envelope, on the screen where you add Recipients, you just need to add yourself and the client/customer. There should be an add Recipient option and I would suggest using the Signing Order. Then make sure to add tags appropriate for each Recipient, each Recipient is color coded and you choose the Recipient in the upper left corner and then add the correct fields/tags on the screen where you drag and drop fields.