Where do i put the clutch fluid?

I have a ford c max and it is sometimes hard to get it into first gear and reverse i have looked it up and i have been told that it might be the clutch fluid i have looked under ther bonnet in the engine bay and i can't seem to find where to put the clutch fluid can anyone help please.

It uses the same reservoir as the brakes do on the C-Max.

Slave cylender