FBX Animation

[shehuinidataoge]

      I am currently preparing to import the FBX file into the bullet, and the entity model has been imported. How should I import the animation information.
      
                            btTriangleMesh* mesh = new btTriangleMesh();
                            int numIndices = fbxMesh->GetPolygonVertexCount();
                            int* indices = fbxMesh->GetPolygonVertices();
                            for (int k = 0; k < numIndices; k += 3) {
                                mesh->addTriangleIndices(indices[k], indices[k + 1], indices[k + 2]); 
                            }

                            FbxTime mFrameTime;
			std::vector<std::vector<FbxAMatrix>> frame_bones_matrix_vec_;
			mFrameTime.SetTime(0, 0, 0, 1, 0, scene->GetGlobalSettings().GetTimeMode());
			for (FbxTime pTime = mStart; pTime < mStop; pTime += mFrameTime) {
				FbxAMatrix lGlobalPosition = pNode->EvaluateGlobalTransform(pTime);
				FbxAMatrix lGlobalOffPosition = lGlobalPosition * lGeometryOffset;
				std::vector<FbxAMatrix> one_frame_bone_matrix_vec;
				for (int lClusterIndex = 0; lClusterIndex < lClusterCount; ++lClusterIndex) {
					FbxCluster *lCluster = lSkinDeformer->GetCluster(lClusterIndex);
					FbxAMatrix lVertexTransformMatrix;
					ComputeClusterDeformation(lGlobalOffPosition, pMesh, lCluster, lVertexTransformMatrix, pTime);
					one_frame_bone_matrix_vec.push_back(lVertexTransformMatrix);
				}
				frame_bones_matrix_vec_.push_back(one_frame_bone_matrix_vec);
			}

The transformation matrix of each frame in each cluster is stored. How can I use these matrices to calculate the mesh, because there is only one mesh, do I need to divide one mesh into multiple submashes and calculate them separately?