Help a GH Noob pls! Sapce Frame creation and modelation!

Hey! I'm currently in a situation where I have to use Grasshopper though didn't use it a lot in order to create a space frame. I found the way to do it, but there are things I don't understand, and that keeps me from modifying 'easier' the structure (in the same time not much time to study it since its for school). What I am intending to do next is to create 2 vertical 'pillars' (always in space frame), placed on the extremities, which would have its starting points(of the lines that generates the frame) at the center of a certain sphere (for exampling for the length 3 spheres..)going perpendicular to the 'ground' (plan x,y).

So I do understand more or less how it works and all, but don't know the use of many functions from GH (started using since september 2014)....

Could please someone help me, ( if possible explain me) how to do it what to use ( using a language for a Noob to understand) 
Thx to whoever responded to my help 'demand' and may you be blessed :D

if it makes it any clear what i need ;)