My suggestion for the easiest way to keep your LDraw library up to date is to download LDView (a separate model viewer program) and configure it to use the same LDraw folder as Bricksmith. LDView has a "Check for LDraw Library Updates" option that will automatically download library updates. It can also search for and download unknown parts in models it opens.
That exe is included in the library for backwards compatibility with older PC programs - you definitely don't need it on the Mac.
You can add parts manually by putting their files in the following LDraw subfolders: /parts, /parts/s (subparts), /p (primitives - bits reused in many parts), or /p/48 (high resolution primitives). You can get unofficial parts (works in progress that haven't yet been added to the official library) at the LDraw Library Tracker. The tracker should link to any needed subfiles for a given part.
If you update your library while Bricksmith is running, you may need to click "Reload Parts" in the Parts tab of Bricksmith preferences for the new parts to become available in Bricksmith's part chooser.
That exe is included in the library for backwards compatibility with older PC programs - you definitely don't need it on the Mac.
You can add parts manually by putting their files in the following LDraw subfolders: /parts, /parts/s (subparts), /p (primitives - bits reused in many parts), or /p/48 (high resolution primitives). You can get unofficial parts (works in progress that haven't yet been added to the official library) at the LDraw Library Tracker. The tracker should link to any needed subfiles for a given part.
If you update your library while Bricksmith is running, you may need to click "Reload Parts" in the Parts tab of Bricksmith preferences for the new parts to become available in Bricksmith's part chooser.