If you already requested the verification code from GMB and haven't yet received the post card from Google with the code, you can request the code again. Here's how:
From the home page Click on "I don't have a code" in the Pending verification section. (See image below)
If for some reason you don't see this message on your home screen, you can click "Enter Verification Code" and then click on the "Mail Again" link. (See image below).