Hi,
Selenium doesn't support locating element under shadow dom. To work with shadow dom element you have to use javascript executor.
1. To start with first have basic understanding about what is shadow dom element and how to check if they are closed shadow dom or open (we can't locate elements under closed shadow dom)
2. Once you have basic understanding about shadow then you are all set you go ahead.
3. Open the websit on chrome browser, right click on the element and copy the js selector which will be used to locate the element over shadow dom. To cross check run the copied content under console.
4. Once you are done #3, use the same js selector as js executor to execute the query which will return you the webelement.
Hope his helps you to get started.
Happy learning,
Arvind