Yes, you don't touch the hierarchy. You find either the part or dummy named extra5/extra6 and click on it to attach it.

Yes you don't ever use the attach function in the hierarchy... You don't really use any tool in the hierachy

Okay guys, I think I got it.

Now my open IV says to go to settings and put the gta.exe directory in the settings thing but when i go to where the .exe is it doesnt give me the option to select it. LOL

Any help. I really want to see if I modded it correctly

You don't select the exe, just the folder

No, you need to select the LaunchGTAiV.exe I think... May be wrong though.

It says .exe but it wont let me choose it. Damn you OpenIV lol

EDIT:

OPEN IV FIXED. MODEL WORKS OMG. MY FIRST EVER CAR MOD WORKS WITH WIG WAG AND ALL!!!!!!

Now, back to original topic, how do i merge two lightbars together in the hierarchy?

Also, how do I select the lightbar as a whole and move it forward/back because whenever I try, it only moves up/down and side/side and it will only move in chunks, like I cannot move the whole lightbar as one.

Un-check the car in the hierarchy so that it disappears leaving the lightbar alone. Then use the Select > All tool, and click on the model. Now turn selected mode on by clicking the text toward the bottom of the screen. Now you can turn the car back on again in the hierarchy and use the move tool. It should now move the lightbar alone.