Get the datasheets for the 15 pin header strips to check their pin spacing. Check that the pin spacing matches the pins on your module. Measure and note the row spacing on the module that you have. Set the grid in the PCB Editor to the row spacing of the headers. Place one strip at one vertex (XY crossing point) in the grid. Lock it in place. Place the second one at the next vertex. Lock it in place. Your header strips are now in the correct positions. You can check this from the grid and using  the Measure or Dimension tools in the PCB Editor. Now you can set the grid to whatever size is convenient for the rest of your PCB layout. You can also set the Origin where you wish. For information about grid and origin settings and locking components please refer to the main Tutorial.