LoadModule and LoadResident actually come with the IconLib_46.4 in the ThirdParty drawer. I didn't know that, but anyway...you have it now.
To install LoadModule, simply copy it to your C directory on your boot partition (which is normally called Workbench or System).
I'm going to download the IconLib_46.4 tonight and test it on my A1200 as it's been a few years since I last tested it. I didn't use it because it didn't seem to speed anything up for me (OS3.1, 8-colour MWB icons - I don't use modern icons with loads of colours or true colour as I prefer MWB).
Looking at the archive though it looks like you can test it just by double clicking on the actual library (icon.library_680xx) and typing 'loadmodule ' before it. It should then reboot and the new icon.library should be available. You can confirm this in a shell or by going to 'Execute Command' in the menu and typing 'version icon.library full' after the Amiga boots up. In fact you can do that first so that you may see what version you are running before applying the update.