Open up iTunes on your MacBook. Go to 'Store' at the top of the page, then click "Authorize this computer." Input your Apple ID information that corresponds to the Apple ID you purchased the apps on your windows computer on. Then, *I THINK* (I don't have it set up right now so I can't check) you go to 'Store>Check for available downloads' and then you'll be able to download your apps to the MacBook.
That command only applies to content that has not already been downloaded. Go to the iTunes Store, log into your account, and click the Purchases link under the Quick Links. From there you should be able to re-download some or all of your purchased content. Note that not all content has been licensed for re-downloading in all countries at this time. You can see what content you can download here:
You can also re-download content using an iOS device.
For full instructions, see:
If you want to get all your content from your iPhone to your MacBook without deleting anything from the iPhone, check out this user tip from TuringTest:
and this page on "How-to Geek":
See also this migrate iTunes library post. Although written from the perspective of PC to PC transfer you can also use the same techniques to transfer the working library from the PC to the Mac and it should appear as the "home" library for your device.