So the title says all : how can I know if I passed/added normals to vbo ?
Is there any visible change on the model or ?
I am new to all of this and still learning and there is a huge chance that this question is damn stupid, if it is sorry 
The question is really obscure and hard to understand. Please provide more detail.
The main use for normals is for lighting calculations, so if you want to know if the normals are present and correct, implement a point light or directional light. The model should be illuminated correctly.