O.M.

Good evening, I am due to start a paid internship later this year. As this would be considered additional income to my existing position as someone who is self-employed, how would I go about recording this properly in my self-assessment tax return next year? I know this query seems a bit too nascent for the time being, but I like being prepared for potential hiccups, especially when trying to properly complete my tax returns! Thank you very much in advance.