Print journals are shelved separately from the books, in the Journals area. At Holloway Road this is on the first floor of the Library. At Aldgate Library you will find current journals on the ground floor, and older issues on the first floor.
They are shelved alphabetically by title, and then by year, so you need to know which year and volume/issue you are looking for.
The following video explains how to locate a print journal on the library shelves.