This is foreign income and meets the criteria for completing a self assessment tax return.
You would need to register for self assessment, if you have never completed a tax return before.
You can register for self assessment at Register for Self Assessment
In the self assessment tax return, you will need to declare your world-wide income.
Your foreign interest would be declared in SA106 (foreign) where you can claim a credit for the overseas tax paid, along with any other appropriate
supplementary pages, as well as SA100, which is the tax return.
You can download and print off the tax return and supplementary pages at Self Assessment tax return forms
If you register for personal tax account (PTA) you can complete your tax return online. Personal tax account: sign in or set up