Track View > Dope Sheet > Track View toolbar > Add Keys
Track View > Dope Sheet > Keys menu > Add Keys
Add Keys inserts a key at the point where you click a curve or a track.
Add Keys is a mode that remains active until you activate another mode. While Add Keys is on, you click in any animation track to add a key at that location in time.
To add keys in Track View:
Click an animation track to add a key.
The location where you click sets the time of the key as measured on the time ruler.
The value of the new key is set by one of the following conditions:
If you are unable to add keys to a track, check the following conditions:
The animation controller must be a type that uses keys. Not all controllers use keys. Examples of controllers that do not use keys include procedural controllers such as Noise.
The animation controller must be a type that uses keys. Not all controllers use keys. Examples of controllers that do not use keys include List controllers, and Parametric or procedural controllers.