Summarize:

Place a framing square near the end of a 2 x 12 (38 x 286 mm) board, leaving a few inches at the end before the end of the square. Use the individual rise and run figures marked on the outside scales of the square that matches your desired measurements. These figures should touch the upper edge of your board.  The short end of the square (tongue) should be on the rise measurement. The long end of the square (body) should be on the run measurement. The board should be at least 12 inches (30.48cm) longer than the planned length of the stringer, just to give yourself some play. Move the square down to extend the run line to the lower board edge, if necessary. This is the outline of your top stair. Slide the framing square along the board so your scale run figure touches the end of your first marked run line. Double check that your rise and run figures are lines up with the top edge of the board and then mark your second stair. Continue down the board, making sure to line up the scale's rise and run figure at the top edge. Mark the new outline and repeat until you have marked 1 extra pair of runs and rises. In order to make the first step the same height as the others, you need to subtract the depth of the thread from the rise, so the finished stair is still 7 inches (18 cm). Simply make another mark to the right of the run line that is parallel and equal to the thickness of the thread. This marks the stringer bottom.
Start laying out the first stair. Mark the outline along the square's outer edges. Lay out the rest of the stairs. Mark the bottom of the stringer.