You need to open the render globals for mental ray at least once (usually).
Then you can go to the text box at the top right of the Maya tool bar and go to Select By Name.
Input: miD*
Hit enter. This will select the miDefaultOptions. Scroll down and there’s a rollout for String Options. The Add button needs to be hit for each attribute you are going to add. So, if you add all of what I mentioned in the response you would need to click it 5 times.
Then each attribute has three fields:
Name
Value
Type
Fill those in as I have them listed here for whichever ones you want to use.
