Hello,

You can read books for this. You can follow the NCERT book as it is so easy and  written in simple words. if at any place you don't understand then you can ask your biology teacher. They will help you out. There are even animations and lectures available in Youtube. You can view them and understand the working.

NCERT is simple from other books for Physics,Chemistry,Maths,Biology. They have explained everything with details.

Hope it helps!