There are a few options for tools to model with, the most common people suggest are either MilkShape (an old, paid, WYSIWYG and simple) and Blender (free, jack-of-all-trades, beginner-unfriendly UI)
If I had to give you a recommendation, it'd be to learn to use Blender. It does everything you could ever need, and then some, and for free, too. The only problem is that it has a steep learning curve and some... unconventional keybinds. But it's worth the effort to learn, imo.
To get models from Blender into to Blockland, look into Port's DTS exporter (DTS being the torque model file type) and Demian's BLB exporter (BLB being blocklands brick format for bricks.)
There's a wealth of information in Modification Help when it comes to modelling and scripting, and plenty on the internet for Blender, so make sure to make use of it!
