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To write the paper in APA format, start with an APA template - a Google search (APA 6th) will find one for you.
After that, start the paper. While writing, when you come to a point to insert a reference, click Reference from the ribbon at the top, then Insert Citation. Select Add a New Source, then enter your source information.
At the end of the paper, use the Reference tab again to selec Bibliography from the dropdown, then insert. That will enter your References page while formatting them correctly for you.