I have answered you in a private mail but for the benefit of the forum I will add the answer here as well.

Currently our FamilyTreeBuilder software doesn't support MAC, but it's definitely in our future plans.

In the meantime you can continue your work using our online editor and tools.

In order to switch your family trees from FTB source to online tree, please contact me at support@myheritage.com

Best Regards,

Shachar

MyHeritage.com support