Need help modifying files: how to display comments to one user only?

I would like to add a little bit of code which restricts the display of comments on a page so only I (admin) and one specific user will be able to see that part of the page.

I guess this is easy to do – some kind of ‘if’ code, which says something like: if logged-in user = admin & specific user ID#, then display this part of the page. for everyone else, hide this part of the page.

That’s the theory, but I have no idea how to write the code!