Self assessment newbie-advice needed please.

[DrSeuss]

I currently work two days a week and pay tax on my earnings at source. I hope to start a small photography business in the next year. Is the correct thing to do to register for self assessment, please? Presumably I would have to keep records of income and expenditure along with receipts?
Thanks

Yes. The tax liability on your new business earnings will depend on how much already earn over the annual personal allowance, from your other job - but you'll be able to state all the facts and figures on the SA form.