If you have SPECIFIC questions, you can ask them here, show what you have tried, and we will help you.
As for where you can learn the material, that's a bit trickier. Maybe do a Google search. A better option, however, would be to get some private tuition to help get you back up to the standard.
If by some stroke of luck you live in Melbourne, Australia, I could do that. Otherwise you will need to look around.