unsureabouttax

Hi, I am a teacher currently on M1 band (£33,075). I have an additional role as a freelance writer which I am registered for as a sole trader. I will make about £600 from this each month. How much tax will I pay on this? I know I need to declare all of those earnings on my tax return but am confused about how this works in addition to my regular, already taxed job. Thanks for any help!