Im assuming THIS is the video you were watching:
What the guy was doing in the video, to gain root access was adding some software called optware to his Pre so that in addition to being able to get root access via a Windows CMD promt, (Once he is at root@castle, he is technically at the linux root) and Novcom, he can also telnet IN (log in from a remote location ie his computer) wirelessly, eliminating the need to plug the PRE in while getting root access. Doing the extra copy/paste stuff he did, enables you to access your PRE from your Computer, using a tool called PuTTy.
Here is the WebOS Internals instructions for that that he is following is:
Next steps - WebOS Internals
Just a small tidbit , on the Instructions page, he shows the following code as 2 separate lines, but the actual page shows it all together. What you have to do, is JUST what he is doing and first copy/paste this:
Which gets you to change directories (cd) to a directory just under the root, called tmp
Then you can copy/paste this:
the wget command is actually a linux utility that lets you download stuff from the web
So AFTER you do all this, you will be able to follow the rest of that video to be able to Shell into, or log into, or PuTTy into your root level of your linux OS on your pre.
WHEN you are able to DO that, then you can start to follow some of the other videos adn WebOS internal tutorials for changing themes, dialers, etc.
I really suggest the first one you try is JUST changing the dialer color. It JUST involves 3 files and is pretty straight foward.
Here is the WebOS internals instructions:
Patch Phone Edit Dialer Theme - WebOS Internals
And here is the matching Video
The FIRST part, Changing the Dialer, is what he is showing on the video. To change the entire theme just involves MORE files, but is basicaly the same process, of getting different image files ON the PRE to make the dialer look different.
Keep at it!

You'll get it!