John Spanitz, you have found yourself in a bit of a catch 22. Unfortunately in order to get to the "Configure Server" button you must first have a functioning WinRM connection to the Exchange Server before the assignment wizard will let you proceed through. These instructions are provided on in the AppInsight for Exchange instructions starting on Page 13 under the section entitled "Manually Configuring Exchange". RC3 will allow you to proceed past this point without a successful test so you can access the Configure Server button in the Application Editor. For now however, you can manually configure the WinRM settings on your Exchange server following the instructions outlined in the document linked above, or switch the node polling method to WMI and use the List Resources or Network Sonar Discovery method for AppInsight for Exchange.
Out of curiosity, why do you prefer to monitor your Exchange hosts via SNMP instead of WMI?