struct Vertex
{
  float x,y,z;
  float nx,ny,nz;
};

const int POSITION_INDEX = ???;
const int NORMAL_INDEX = ???;

glBindBuffer(GL_ARRAY_BUFFER, vertVBO);
glVertexAttribPointer(POSITION_INDEX, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), offsetof(Vertex, x));
glVertexAttribPointer(NORMAL_INDEX, 3, GL_FLOAT, GL_TRUE, sizeof(Vertex), offsetof(Vertex, nx));

glEnableVertexAttribArray(POSITION_INDEX);
glEnableVertexAttribArray(NORMAL_INDEX);

glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexVBO);
glDrawElements(...);