I am trying to scale a model in OpenGL, but I dont know where to start, I am trying using glScalef(), but I dont know if is in this way, I dont know alot about openGL, I know more about theory(That I have to multiply my vector by a matrix, but I didnt found any good tutorial about this)... My code is that:

bool res = loadOBJ(object, vertices, uvs, normals);
indexVBO(vertices, uvs, normals, indices, indexed_vertices, indexed_uvs, indexed_normals);

glGenBuffers(1, &vertexbuffer);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
glBufferData(GL_ARRAY_BUFFER, indexed_vertices.size() * sizeof(glm::vec3), &indexed_vertices[0], GL_STATIC_DRAW);


glGenBuffers(1, &uvbuffer);
glBindBuffer(GL_ARRAY_BUFFER, uvbuffer);
glBufferData(GL_ARRAY_BUFFER, indexed_uvs.size() * sizeof(glm::vec2), &indexed_uvs[0], GL_STATIC_DRAW);


glGenBuffers(1, &normalbuffer);
glBindBuffer(GL_ARRAY_BUFFER, normalbuffer);
glBufferData(GL_ARRAY_BUFFER, indexed_normals.size() * sizeof(glm::vec3), &indexed_normals[0], GL_STATIC_DRAW);

// Generate a buffer for the indices as well

glGenBuffers(1, &elementbuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementbuffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices.size() * sizeof(unsigned short), &indices[0], GL_STATIC_DRAW);

// 1rst attribute buffer : vertices
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
glVertexAttribPointer(
    0,                  // attribute
    3,                  // size
    GL_FLOAT,           // type
    GL_FALSE,           // normalized?
    0,                  // stride
    (void*)0            // array buffer offset
    );

// 2nd attribute buffer : UVs
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, uvbuffer);
glVertexAttribPointer(
    1,                                // attribute
    2,                                // size
    GL_FLOAT,                         // type
    GL_FALSE,                         // normalized?
    0,                                // stride
    (void*)0                          // array buffer offset
    );

// 3rd attribute buffer : normals
glEnableVertexAttribArray(2);
glBindBuffer(GL_ARRAY_BUFFER, normalbuffer);
glVertexAttribPointer(
    2,                                // attribute
    3,                                // size
    GL_FLOAT,                         // type
    GL_FALSE,                         // normalized?
    0,                                // stride
    (void*)0                          // array buffer offset
    );

// Index buffer
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementbuffer);

glScalef(10, 10, 10);

glDrawElements(
    GL_TRIANGLES,        // mode
    indices.size(),      // count
    GL_UNSIGNED_SHORT,   // type
    (void*)0             // element array buffer offset
    );

glScale works on the previous system where you have fixed unction pipeline.

I can assume from your code works with shaders.

The correct way:

You calculate your matrices:

That I have to multiply my vector by a matrix, but I didnt found any good tutorial about this.

http://www.opengl-tutorial.org/