how to animate face on rigged character

How would I animate the face of a asset character that has preset rigged animation on it ?

I inserted an asset character that was already built then added the walking preset rig to make it walk, but now I'd like to animate the face as it walks. This is an asset in adobe. The yellow circle is the part Id like to animate. 

 this is the layer with green on the timeline is the walking animation but when i go into the layer of the face and animate it , it doens't show up when he is walking 

this layer is the facial one. by default it only has one keyframe on the first section of the time line. 

all the extra keys are me adding animation but they don't show up when the character is walking. 

I can't access the face when the character is walking