If you started a 'Work with Client' D49 type then you will not need to manually send the design to your client. Your designer will send the design to your client in an email (with viewing and commenting instructions) and they will send it back via the slideshow.
If you started a '1st Draft' D49 then you will need to send your client the design once you have approved it. Follow the steps below to send it.
Hover over the design slot and navigate to the Sharing icon in the middle. From there, select "Send to Client for Comments".
You will receive an email when your client has made comments through the proofing slideshow.
Tip: Select the 'Work with Client' D49 type when you being and your designer will send the design right to your client and work with them on revisions.