Hi
As your self employment income is more than £1000.00, you will need to declare it in a self assessment tax return.
You will need to register as self employed at
Set up as a sole trader: step by step.
In the tax return you declare your world-wide income and claim personal pension relief by declaring the gross figure paid into your pension pot, including the tax relief claimed by your pension provider.
This will give you additional tax relief as you are higher rate.
Thank you