There you are. Welcome.
You might run into some problems playing some PC scenarii since most of these are already updated to the 1.10 Patch which is not, and probably won't be ever, available for Mac.
Just try and if it says " File can't load ", you'll know why... For info, we're still under the basic... 1.0 application.
Now my suggestions are mostly for designing but that could help you playing customed scenarii as close as the creator wanted it to be.
So far, I have been adding to the original Mac AoE3 with great satisfaction:
AoE3 Reyk's editor
Designer's Mod for Patch 1.09 ( But be aware this is not the official ES 1.09 patch. )If you need some help for Reyk's editor installation, try this.Now for info: ThisBeside when you've done with all of this, you could always tried the first Mac scenario but wait just a couple of days as I'm uploading the N°2 tonight... I hope.Now about playing:
the file extension of a downloaded scenario ( to be dropped into your Documents/My game/Age of Empires 3/scenario directory ) should be " .age3scn "
Be aware there is a new expansion called The War Chief ( don't d/l anything TWC, .age3scx? ) which is... not available for Mac!
You might run into .exe files, Stuffit might be able to open some of those... sometimes. The queue thing? No idea beside the shift button.
About the KoGar's "40 Cards Per HomeCity" mod, that might work. It's a .zip file, so just x2 click it and you'll get a read me and a folder with lots of HC files. I suppose you should just copy those files following the read me indications.
If you've got some spare room on your comp, I strongly recommend to make a copy of the original 2Gb AoE3 application! ( not the documents folder! ) to come back to it in case of troubles.
Very important point about AoE3 Mac: most of mods, such as KoGar's "40 Cards Per HomeCity" mod, have to be installed within the application itself ( not the documents folder where your savegames and scenarii are stored! ).
In order to do this: ctrl-click on the application, scroll to open package and follow until you reach " Game Data " where you'll find some interesting folders, to drop mods in.
A bit tricky, but works great.TWC for Macs? Never in a lifetime.