Self assessment help?

Hi there, I am in a somewhat weird situation job-wise, and I was wondering if I could get help with the upcoming self-assessment deadline. I have two jobs. One at a company where I earn 20k a year and have my wages taxed on the payslip, i.e., they show what's been taken out, but I also work as a journalist, and I make less than 10k in total. So, as a tax newbie, I was just wondering if I have to do a self-assessment form, and when I declare my earnings, I add both jobs' incomes up or just the writing income. Sorry if this is complicated

Hi EdSpen,
You will need to register for Self Assessment to show both sources of income by tailoring the tax return.
You can register for Self Assessment here:
Check how to register for Self Assessment
How to tailor the tax return here: 
How do I tailor my Self Assessment tax return?
This further guidance may also help completing the whole tax return:
HMRC email updates, videos and webinars for Self Assessment
Thank you.