Don't overuse first-person pronouns. Although APA allows for the use of first-person, pronouns such as "I" or "we" should be incorporated into your paper sparingly.
Cite your past work using the following format: (your last name, year of publication). The parenthetical citation should be placed immediately after a reference to your past work has been made. For example: "A previous study suggests that there may be a link between staring at a computer screen and depression rates (Smith, 2010)."
You may also cite yourself by including your last name in the body of the text and placing the publication date of the work in parenthesis next to it. For example: "According to a study by Smith (2010), there may be a link between staring at a computer screen and depression rates."
Don't forget about proper referencing. In addition to the in-text citations, you should include the past work that you cite in your reference list. Reference your past work using standard APA formatting guidelines.