All non-fiction are organised using the Dewey Decimal system. Simply look at the chart on the wall above the main desk, find the category number and then find the matching number on the shelves.
Check your ZPD (Zone of Proximal Development) which helps you to choose books which are easy enough for you to read independently but are still challenging. Look up the colour of your Zone and find a book on the carousel with that colour on its spine. Books are placed in alphabetical order using the first letter of the author's last name.