You can get LDView from ldview.sourceforge.net. LPub doesn't do any rendering. It requires a renderer to be installed (like LDView).
I don't remember off-hand where Bricksmith puts the parts library, but it might well be inside the Bricksmith.app app wrapper folder. Wherever it puts the parts, you need to point LPub and LDView to that folder. When LDView first launches, it asks you if you already have the parts library installed. You can either point it at the LDraw folder that Bricksmith sets up, or you can tell it you don't have the library installed, and let LDView itself download and install the library. If you have LDView download and install the library, you'll have to point LPub and Bricksmith at the folder that LDView creates. I'm pretty sure that a parts.lst file is in the default LDraw library.
Parts that you can't find in Bricksmith are either not made yet, or not official. You can download unofficial parts from http://www.ldraw.org/library/tracker/. Most people recommend downloading unofficial parts into a different directory. Official parts go into <LDraw Directory>/Parts. Unofficial parts can go into <LDraw Directory>/Unofficial/Parts, and I believe Bricksmith will automatically see them. If you do download an unofficial part, make sure to also download all of its companion files. Alternatively, simply open the main file that you download in LDView, and it will automatically download all the missing companion files into <LDraw Directory>/Unofficial.
I don't remember off-hand where Bricksmith puts the parts library, but it might well be inside the Bricksmith.app app wrapper folder. Wherever it puts the parts, you need to point LPub and LDView to that folder. When LDView first launches, it asks you if you already have the parts library installed. You can either point it at the LDraw folder that Bricksmith sets up, or you can tell it you don't have the library installed, and let LDView itself download and install the library. If you have LDView download and install the library, you'll have to point LPub and Bricksmith at the folder that LDView creates. I'm pretty sure that a parts.lst file is in the default LDraw library.
Parts that you can't find in Bricksmith are either not made yet, or not official. You can download unofficial parts from http://www.ldraw.org/library/tracker/. Most people recommend downloading unofficial parts into a different directory. Official parts go into <LDraw Directory>/Parts. Unofficial parts can go into <LDraw Directory>/Unofficial/Parts, and I believe Bricksmith will automatically see them. If you do download an unofficial part, make sure to also download all of its companion files. Alternatively, simply open the main file that you download in LDView, and it will automatically download all the missing companion files into <LDraw Directory>/Unofficial.