The best way to find someone's Youtube channel is by searching directly on Youtube with the built-in search bar. The search brings up the channel you are looking for as well as videos related to the search.
After first going to Youtube and entering your terms into the search bar, narrow the results, if necessary. By clicking on the Filters button in the top-left side of the search screen, a drop-down menu shows up, allowing you to narrow your search results to video, channel or playlist. You can also sort the results by the number of views and user ratings.