The 7th edition of APA's Publication Manual provides guidelines for formatting papers. APA makes a distinction between student papers and professional papers (papers being submitted for publication). This guide outlines the requirements for student papers.
Student papers usually include a title page, the text of the paper, and a reference list. There will be page numbers at the top right of all pages, with the title page as page 1.
The major change from the 6th edition of the Publication Manual, is that a running head is no longer required on student papers. However, your professor may still require it, so follow the directions of the assignment. For instructions on creating a running head, see here.