How to access a controller inside a folder

Hello everyone i am pretty new to cakePHP however i can create a small CRUD application, so i was trying to create different users and to better organise the app i created a folder lets say for Admin and placed the controllers there…however i cant access them…do i have to change anything in the routes.php file as well?
thanks in advance…am using cake 3.3.12

You can take a look at

thank u so much…its worked, was having trouble finding that exact part in the book