Manipulating vertices in three.js

I loading a template body model in fbx format. Which contain a universal_mesh what is skinnedmesh for entire body. i want to change the face structure for that need to update data of face vertices. from server i get uv point of face those data need to be changed and vertices data which need to be update. but this data is from unity which has indexed geometry. i m searching a uv point that i get from server in faceGeometry.attributes.uv.array finfinf its index and replacing the vertices data at tat index in position array but result is not proper face is coming deformed. Any way to alter face geometry correctly??