(1)  To determine where the partings will start,  take a comb and place it at the top back of the head.  Where the comb leaves the head is where the parting will start.
(2)  Make a parting from that point to the top back of the ear.
(3)  Determine where you want your first track to go. The first row is usually from the back of the middle of the ear all the way across to the back of the middle of the ear.
(4)  There are many invariable in installing the strands.  If the hair is thin and shorter you may want to "pack them in" the first 2-3 rows; this describes installing the extensions right next to each other across the row and section the next row right above the previous row leaving no hair out of the extensions.
(5)  After establishing weight for the first 2-3 rows, you can now "brick row" the extensions; this described installing the extensions on every other piece of hair and on the next row above the row you've just installed you will install an extension above an strand there there is an empty space with no extension installed there.  The effect will be like a checker board; every other strand will be installed above every other but moved over by one space.
(6)  Continue up the head until you reach the top leaving enough hair at the top to cover the last row of extensions.