This isn't a question i hear often.
right click and 'hold' the sphere or nurbs object
click on an existing isoparm and hold (they are the blue lines in either direction)
drag to desired position and release ( a dotted line is created)
Shift and select for multiple isoparms, but they must be going in the same direction.
in the modelling menu, slect edit Nurbs and select insert isoparm.
if you need this often, hold shift and ctrl key then click it, this will move it to your active shelf for faster use.
And after calming me down with some orange slices and some fetal spooning,
E.T. revealed to me his singular purpose.
--TOOL, 10,000 Days---