firstly you start aom and click more, then recorded games. You dont open the file with anything but aom. Assumming you have aomtt extract the file to here
Documents and Settings\My Documents\My Games\Age of Mythology\Savegame
I would recommend going to www.aotsanctuary.comfor games. they are not zipped and they are expert games mostly. aomtt takes only .rcx aom take rec and they wont work cross platform. and they have different save game folders C:\Program Files\Microsoft Games\Age of Mythology\savegame for regular aom
R.I.P Shiva