Recovering tax paid on US share sale

I have US shared gained as part of my employment. When I was given these shares they were taxed as a benefit. They were sold as part of a takeover and the US government has taxed the sale. I have been told that I can recover this tax through self assessment as double taxation. How is this done in the self assessment return?

Hi,
In the Foreign Section when filing your Tax Return online, you can claim for Foreign Tax Credit Relief.
Tax on foreign income
Thank you.