The running head includes the paper's title and appears on each page. You might need use a shortened version of your title because the running head should contain fewer than 50 characters, adding up all the letters, spaces and punctuation. Left-justify the title in the header and capitalize all the letters. The header on the title page includes the term "Running head" (without the quotation marks) and a colon before the title. Subsequent pages have the title, in all caps, without the "Running head" introduction.
The other element in an APA header is the page number in case the manuscript pages get separated when submitted. The page appears right-justified on each page, beginning with the title page as page 1 and running all the way through the References pages. Use Arabic numerals with no "p." or "page" or other indication before the number. Your name doesn't appear in the header so the manuscript can be read in a masked review with the readers unaware of the author.