Why haven't your PARENTS done this!? This is THEIR job!
Online programs aren't dependent on the brand of computer you have. Anything you find online should work with your mac. What matters is when you BUY CDs with the programs to load. THAT's when they are specific to your system.
Are you taking A CLASS? Because there should be materials attached to them.
There are many online text books/programs...just search "learn French online free".
The thing is, if you don't have a teacher, you will likely struggle with understanding things. And you won't have anyone to ask. If you don't understand the concepts, the people here are hit-or-miss. Some know how to explain things. Some have no clue. Some will answer incorrectly, just to confuse you. You need to sign up for a COURSE, if you haven't done so, yet. There are MANY online schools.
Livemocha.com will teach you some good basics, but the grammar (which is what most school courses test you on) is really poor.
french.about.com will give you some vocabulary, and some good grammar with some exercises to practice, but if it's the first time you are studying a language, it probably isn't enough.
Based on what I know of the Spanish course from Colby College, this should be good. http://www.languageguide.org/french/grammar/
Do your own search.
Try to find textbooks online. Big Textbook companies include McGraw Hill; Harcourt, Brace Jovanovich; Scott-Foresman. See what you can find on those.