Hi,so I'm taking this medicine for pimples which makes my skin very dry and my scalp is very dry.. its itchy I don't know what to do about it can anyone please help

Not much. Try using a dandruff shampoo. They've usually got a bunch of scalp moisturisers in them. The drugs you're taking are drying out your skin to prevent the acne, the side effect is dry skin elsewheres.