From PhoneServer, click on Edit -> SMDI Link. Check the "SMDI Link Enabled" box, and select the appropriate "Com Port" and "PBX Type". Then click OK. You should be prompted that the changes will take affect the next time PhoneServer is started. Click OK again.
Now, from PhoneServer again, click on Edit -> Configuration. Select the "MWI Settings" tab, and check the "Enable MWI" box. Enter the time you want for the "Update Period". Then select "Use In-Band Dial". You then need to select the line number from the drop down list, that you want to use for the MWI application. Usually the last port. Then switch back to "Use SMDI Link".
Set the Unread Handling to "Match Inbox (Single Folder)".
Now click on "OK", and restart PhoneServer. You should now be set up for MWI, using your SMDI Link.