One beauty of the opensimulator is import and export capability. With a viewer like imprudence we can easily build up the virtual world. It is very good way to start tutorial from opensim artist home. A good collection of OpenSim compatible creations can be found from here. Those are available for download and just need to give the path of .xml file in extracted folder.
Go to file-> Import+Upload of the viewer.
It will take sometime to upload the file. Once it is done, we can placed it in a preferred position. The other important thing is that we can set up any reusable virtual environment instantly. I have download one of these virtual terrain and using a single command I was able to load that terrain.
terrain load terrain-apple.png
Finally it is also possible to reuse available world rather try one by one. I try the virtual world called "Tiki Summer Sim" on my own risk. It really easy to be use and just a single line of command is required. Just past with load function + whatever the file name as bellow.
load oar xxx.tgz
Make sure that what is exactly needed by the simulation. Unnecessary beauty of the scene will be reduce the simulation performance significantly. This example simulation has been consisted around 4275 primes which consumes 1GB memory.. :)