Here is a quick rundown what I have tried so far:
1. Installation: they offer both standalone and update site, I just installed through update site following their instructions. I am on Eclipse 3.7.1, btw. I also got lua and luarocks installed through Homebrew (by default they are installed in /usr/local/bin).
2. Create a new Lua project: create a new Lua project, add source files under src, similar to the typical Java projects.
3. Ready to run? I feel stuck at this step at first since there is no launch configuration that allows me to configure the local Lua environment. After running through several threads, it seems Koneki does not support launch configuration yet. It only supports "remote debug launch configuration".
But the developer also provides this workaround using "External Tools" and I got it to run and show the results in Console View. This is the sample configuration (you need to select the main.lua before run this external tool configuration). For the meaning of Eclipse variables like ${workspace_loc}, ${resource_loc}, see Eclipse external tools documentation.
Many thanks to the LDT developers for this nice IDE. I wish the launch configuration can be added so beginners like me can get started with Lua and LDT quickly. Also, I wish the configuration of debugging and remote debugging can be integrated into LDT.