Thanks Flan747, sorry if you have already posted this elsewhere, why are you on 4 sachets? It's a lot of gel. Maybe you're not a good gel absorber and could benefit from patches?
If you really need 4 sachets here's the instructions.
How to apply the gel
Sandrena should be rubbed gently on dry and clean skin. It should not be swallowed.
Where to apply the gel
Do not apply the gel to your breasts, face or on irritated skin.
Apply the gel to your lower body or thighs. Apply the gel to a different side of your body each day.Follow these instructions:
1. Apply the gel once a day to the skin on your lower body or thighs.
2. Spread the gel over an area 1–2 times the size of your hand.3. Allow the gel to dry for a few minutes.
4. Wash your hands after applying the gel. Avoid contact of the gel with your eyes. The gel may irritate your eyes.
5. Do not wash the area where you have applied the gel for at least one hour.
Not sure what they mean by 'lower body', though. Buttocks?

AM or PM, whenever is more convenient for you.