LOD is relatively straightforward but it's also of limited usability.
You need to follow a strict naming convention for LOD meshes: typically, "LOD_0" for high, "LOD_"1 for medium and "LOD_2" for low.
Your LOD models need to each be single mesh objects (no groups or hierarchy).
You need to have all LODs in the same scene when exporting.
From there it can get a little dicey because Reloaded doesn't parse out names like it should and is easily confused. So, LOD can easily be broken causing the wrong LODs to display if you aren't really sure of what you are doing when it comes to export options and scene hygiene. Depending on the software and how it organizes meshes and the scene root, it may not even be possible to export working LODs. Also be advised that (from what I have last heard) that the lightmapper uses the lowest LOD. Which may or may not look awful.
Gigabyte P67A-UD4-B3, Intel Core i7 2600K, 16GB Corsair DDR3, EVGA GTX 970 SC, Win7 Pro 64-bit SP1, Primary monitor @ 1920x1080, secondary monitor @ 1024x1280