Well, maybe if you give some information, I can tell you where to place the mod..
Which mod are you trying to install?
Vehicles go into addons.
Paint colours go into: C:\Program Files\Blockland\base\config\server
decals go into the appropriate folder (depends if face or body decal)
which is: C:\Program Files\Blockland\base\data\shapes\player
Maps go into: C:\Program Files\Blockland\base\data\missions
But, those all depends on how the maker zipped their files
Anyway, hope that helps.