You would have to extract the matrix from the affine transform and set it to your OpenGL shader. Unfortunately, as far as I know, you cannot get the matrix from the affine transform so...

Fortunately for you, translation and scaling matrices are very simple.

Translation : 1 0 0 tx Where the translation vector is (tx, ty, tz)

0 1 0 ty

0 0 1 tz

0 0 0 1

Scaling : sx 0 0 0 Where sx, sy, sz are the respective x, y and z scaling coefficients.

0 sy 0 0

0 0 sz 0

0 0 0 1

However a sound knowledge of transformation matrices is essential for advanced OpenGL so I would advice a bit of research. I found

http://www.wildbunny.co.uk/blog/vector-maths-a-primer-for-games-programmers/ to be an excellent starter.