ACP -> Configuration -> Settings -> Google SEO URL -> change "Thread URL scheme" to
{url} (but it's going to result in conflicts so I don't think you an use it like that).
EDIT: as I thought, you can't, read this:
http://community.mybb.com/thread-138627-...#pid999846 You can only change it to another identifier, like
t-{url} so the links will be
http://www.domain.com/t-threadname
Then go to ACP -> Configuration -> Plugins and do everything stated insiide Google SEO description (.htaccess modifications).
If you use {url} for threads, then you have conflicts. (is Forum-Name a forum called "Name" or a thread called "Forum-Name"? Is admin the Admin CP or a thread called admin?)
So unless you resolve those conflicts (such as by renaming the admin cp folder to admin.cp, and changing Forum-, User-, Announcement-, Event- etc. to f. u. a. e.) and not having any other subcontent without dots or similar characters that are filtered by Google SEO...
Not recommended, you risk URL breakage.