To understand the concepts easily, firstly, you need to pay your best attention to the class and listen carefully to what your teacher teaches. This is really a very important step. Everything just gets absorbed into your head when someone teaches you.
Whenever you don't understand, what is taught in the class by the teacher, take your friends help and ask them to explain the tough parts. The easy ones, I am sure, you can understand, by reading on your own.
Even then, if you don't understand, go to the teacher and make him/her explain to you with full clarity and precision. You can consult your seniors too.
When you've understood something thoroughly, you've automatically almost learnt that!
Learning something by heart without understanding the base concepts is something really futile.
Concepts in chemistry are really very simple to learn if we make our attempts with required levels of interest and concentration.
When something is not getting into your head, please DON'T try to learn it by heart by reading and reading continuously. Rather, take small breaks, make your mind relax and then come back and try to draw in the information keenly.
Putting down the matter on a paper separately and/or explaining to your mom/dad or siblings or friends also helps!
If one way doesn't work, don't get disappointed. There is always a way for you.
You just need to work hard and treasure it out.