I decided to ask my question here because of the intense interest in Google Voice for the Obis.
I found the following on the Google Voice forum that addressed my problem:
1. Make at least one call from the "call phone" feature in Gmail/Chat.
2. In GV website | Settings (under the gear icon) | Phones, add Chat as a forwarding phone
3. With Gmail open in another browser window and Chat logged into, initiate a call from Google Voice.
I had already done 1.
I logged into gmail, then went to gv and discovered that the Chat check box had appeared. I don't know if logging into gmail, revealed the Chat check box or something else did...