Place the paper in the printing area. Tape around the paper in a border, but do not tape the paper itself. This will create a reference for the paper's placement should it move during the printing process.
Lay the screen over the printing area, and apply masking tape to the table either around the entire frame or just around the corners. At least two opposing corners should be marked.
Hold the screen in its proper place and secure the screen to the table hinges. The tape used to border the screen will tell you if the screen has been jostled so that you can adjust and re-secure as needed. Also, the marks ensure consistency of placement each time the screen is cleaned and prepped for a new color.