In iD, below the main list of layers there's another list of "Overlay"s, it should be in there (eg 7th of 9 in that list for me).  Turning that on should show you blue lines for the land ownership boundaries.  Then scroll further down the same panel to the bottom to get a grey box with 2 numbers in the middle.  You drag with the mouse on the grey area to move the current imagery (eg Esri/Bing etc) relative to the blue lines.  Try to ignore all of the OSM mapped features and anything on the imagery well above ground level, eg if you re-edit here, you'll see a nice rectangle of blue lines matching the low wall around the lighthouse group of buildings.  (The more the imagery isn't vertical, ie you can see some of the side walls of buildings, the more careful you have to be to match to ground level features eg the bases of walls.)  And ignoring the OSM mapped features takes some practise (in JOSM you can turn off the OSM data while you align but not in iD I think).  Hope this helps. Cebderby (Clive)