First try to understand what the content is about the put it into practice like exam question or past papers ( try issac physics, maths genie or physics and maths tutor <- has a lot of questions ) and just keep practicing. You will improve.
Use the specification I recommend using anki for spaced repetition (formula, definitions, etc) Do lots of questions - isaac physics and the textbook mixed exercies/review exercises have lots of good, specification-relevant questions
lots and lots of practise questions!!! for subjects like physics and maths, practise is the best way to improve. esp for physics the questions will seem really tough at first but u will improve as the year goes on!! do ur usual revision for the content like flashcards and mindmaps etc (whatever works for u) and then lots of practise questions (isaac physics is great and also physics and maths tutor) hope that helps