Cetlment is at (128, 128, 45) in the Main Grid - an easy way to reach it is to search for Cetlment in the map and then teleport there. Bear in mind that the SecondLife search is case specific.
Once you're there, don't confine yourself to the ground or to floating around in the water feature – there are floating seats in the clouds and buildings in the sky if you look above you, plus a growing number of structures in the water arond the island.
Jacquie is the owner of Cetlment island. She has set us up with an area where schome folk can build stuff . There is also a noticeboard so we can share info with folk (click on the board to get some info).