wavelab 5>Options>Recording pulldown menu>click on whatever the mme shows up as (make sure it's plugged in)
In the "Record" dialog box (when you've pressed record) Select: Select File to create "named file" and then choose the settings you want. I usually select the auto split feature to make sure, if anything goes wrong I don't lose the entire recording, but the one it was presently writing. Like auto split every 30 mins or so. Whatevuh.
You may also select the Input device in the Record dialog box, by selecting "Audio Card" then clicking on the ... box next to it and choosing what is available from there.