Question on Zmodeler

Hello! I am a very new comer to Modeling!
OMSI Motivates me to build a bus... so......

I get trapped here .... actually having a lot to ask =w=
But I would ask later.

I am modeling using Zmodeler (commonly used in MM2)
And creating :

I am finding the way to link the front and the LHS ... i dont know which tools to use?
Attach? Connect? Weld? I saw these on the Zmodeler website's tutorial.
In fact I am not very sure how to use them, just use a bit common sense to build it ...

Thanks for anyone's help ;D

Notes:
In fact it is a Dennis Enviro 400. A newly came Hong Kong Bus. And it's my fist project.
If it can be developed and go into more detail (Even in game)
I will post it to the Showroom
May be it get a chance to release .... so far .... let me get familiar with ZM first -.-

Notes 2 : It is ZM 2.x, not ZM 1.7 something...

1) Select "Object Mode" in the top bar.

2) Desactivate select mode in the bottom bar.

3) On the operation box select: Modify -> Attach.
4) Click on the first part of model.
5) Click on the second part of the model.

Regards

Thanks ;D
I got it integrated.
But the problem now is that i dunno how to merge the edges..... :/

Look this Video tutorial, shows the creation of a bus on zmodeler.
http://18wosbusmania.blogspot.com/2010/12/tutorial-zmodeler.html

Regards.