Since Punchout is mostly a B2B integration between your catalog and your customer system you will have to work with their team to connect to it, this process requires delivering appropriate credentials to be plugged into.
Inside the Credentials section you will find all the parameters required in order to connect your Store to any CXML Procurement System, you can copy and paste them individually by clicking on the icon that shows up to the right when hovering over, or use the "Send Tab" to type an email address where to send the Credentials.
Send Tab:
Type an email and click "Send Credentials" to send an email with all the credentials to the customer you are interfacing with:
Once your customer has plugged into their procurement system normally a round of tests will occur, you can monitor those tests manually or ask for help to our team in order to jump through any particular hoops required for an integration.