For the first time since they were released last year, Apple has released an AirPods firmware update , which runs from version 3.3.1 to 3.5.1.
Of course, do not expect big changes, since at the moment there has been no significant news reported in this new firmware, so Apple should have simply applied some stability improvements.
First AirPods Firmware Update Available
As for how to update your AirPods, if you are asking the answer is that they update themselves , being the only requirement that are in their case and near the iPhone with which they have been linked previously.
In this way, and taking into account that no major changes are appreciated, my recommendation is that you forget the update and continue using them as usual until they are automatically updated.