UK Tax Advice needed on a second income?

I have started making money decent money through Clickbank for the last two months but I also have a full-time job. How do I go about paying tax on earnings in the UK?

Do I need to register with HMRC as sole trader or just setup a limited company?

I really have no idea and don't want to be arrested for tax evasion as I already have ongoing legal problems.

I have cheques from my current earnings but have not deposited them in my bank account yet because I am not sure how to proceed?

Thanks

just dont hide it and you will be fine