Mechjeb problem (v.1.2.1)

[nyugnep]

So I am fairly new to KSP, I have yet to update it to 1.2.2 version (limited internet) so I am playing on 1.2.1 and I don't seem to be able to start MechJeb. I downloaded the update from sarbian and i moved the mechjeb folder into gamedata. I launch up the game and it doesn't seem to be working so I am kinda stuck. What am I doing wrong? Eventually, are there any other mods that help with delta-v calculations?

Edit: I've been pointed out on reddit to describe my problem. The problem is that there is no sign of existence of the mod. Neither in sandbox/career VAB/In-flight. 

Edited December 11, 2016 by nyugnep

[Gianni1122]

With MechJeb, you have to attach the "part" that comes with MechJeb to your ship or it won't work

KER will calculate delta-v