To drag a series down.. ok try this on a new spreadsheet
Cell A1 type "1" (just the number 1), hit return
Type "2", hit return
Type "3", hit return
Then with the mouse select the three cells. While the three cells are selected (no mouse buttons down), put your cursor in the bottom right corner of the rectangle. It should turn into a black crosshair. Click and hold; drag down down down down. Release
It should fill in cells going down with 4, 5, 6...