Get the oxygen updater app from play store and then flash the latest update.
But this is not oneplus apps officially
This is an incremental roll-out and it is limited to some users in beginning to ensure there are no bugs before rolling out to others.
You might get this update within a week.
Its perfectly safe i have used it many times.
If you want official update then wait for the roll out.
I have update my nord this morning with Oxygen updater incremental to 10.5.8 september patch and manualy update the Google play to September. There is no danger to update by that way and it's give you from first minute the newest updates they are official
Please read and use the official update thread for any questions about the update. The reason is explained in the first post
The final round of IDEAS is starting! Share your OxygenOS-related idea now.
by Zach X., 2020-10-27