Bluetooth streaming now seems to be enabled for some Google Home users, as people are reporting that the feature has popped up in their Google Home app under the settings menu as a new option labeled "paired Bluetooth devices." Tapping on this option opens a new page that tells you which devices are paired with the speaker and if there are none or if you want to pair a new one, a button allowing you to enable Bluetooth pairing mode sits in the bottom right-hand corner of the screen which should initiate a search for any nearby devices that have Bluetooth turned on.
It's not clear if Google is now officially rolling it out to everyone but that seems to be the case, though having said that it's also likely that some users still won't see this option in their app which means Google could be pushing the feature out in stages. If the feature is hitting users on a gradual basis then it might still be a few days before it shows up for the majority of users with Google Home speakers.
Reportedly users don't need to be part of the recently launched Google Home Preview Program but it is likely that you will need to be on at least firmware version 93937 for the Bluetooth option to show up in settings, keeping in mind though that as mentioned above it may take some time for the feature to surface if it's not already there. Another thing worth paying attention to is that the audio may be laggy as this has been the case for some, so even if you can pair Bluetooth devices you might not end up with the best audio experience at the moment. It's not clear what is causing the audio lag but if it is an issue that is more widespread than a handful of users then Google may hold off pushing this out on a more wide scale and send out a fix first. Bluetooth support for the speaker has been a bit of a wait for those who have had the device since last Fall, though Google didn't officially announce that the feature would be coming until Google I/O earlier this year. Now that Bluetooth streaming appears to be going live though, users will have another option for streaming music, as Play Music purchased songs were added just recently as a means for streaming audio. It also initially was thought that Bluetooth support was rolling out to the speaker as early as June 29th though this seems to have been for a much smaller number of users at that time with it now likely being a full rollout.