If you have the deluxe version of FSX which contains the sdk tools when installed from disc there is a default object placement tool which comes with it that i use ,for me its been the most simple option of placing objects ,i have answered this before in this topic here and some instructions on how its installed and activated .
http://nzff.org/forum/viewtopic.php?t=...bject+placementif you would like to place anything from my scenerys ie floatplane base here is the guid you will need 7D0E82354E6870C1D73F09B64DEFE6C1 FLOATBASE
11B868CC40C648AC33B39298806CCA4A Helipad which both start with 0 on the list of objects that you will be able to place
once placement tool is working you start the object placement tool via the FSX alt/menu in game and you will see a box pop up and the word action in a drop menu ,click that and on the drop down select the scenery option then the drop down on below that has the guid codes and objects that you will be able to flick through real time view and add to your scenery .
once you have placed the objects click mission tab at the top left and save scenery tab ,this saves a XML doco which you will need to drop on the BGL.exe file that is found in the sdk
,place the bgl file it creates from the xml into the scenery folder in addon scenery load up where you placed them and they should be there etc ..
hope this helps abit
mike