The APA Publication manual shows the upper right hand corner of the page for manuscripts. On page 288, Section 5.06, Page Numbers and Manuscript Page Headers, it indicates "Number all pages, except artwork for figures, in arabic numerals in the upper right hand corner."
Note though that the manual also indicates that schools or institutions may vary the page formatting for submissions. Specifically, in section 6.01 on Page 322 in discussing theses and dissertation preparation: "...theses and dissertations are submitted to the student's graduate school, not to a journal. Therefore, they must satisfy the graduate school's specific requirements, even if these requirements depart from the style outlined in the Publication Manual."
The short answer is the upper right corner unless your school specifies otherwise.
R.F.B. - Illinois
Note though that the manual also indicates that schools or institutions may vary the page formatting for submissions. Specifically, in section 6.01 on Page 322 in discussing theses and dissertation preparation: "...theses and dissertations are submitted to the student's graduate school, not to a journal. Therefore, they must satisfy the graduate school's specific requirements, even if these requirements depart from the style outlined in the Publication Manual."
The short answer is the upper right corner unless your school specifies otherwise.
R.F.B. - Illinois