I did mine this way. If you're on a wireless network, then make sure they're both on one network. In your Windows computer, right click the drive you want to share and click "Sharing and Security". In the "Network Sharing and Security" section, click the "Share this folder on the network" checkbox. You may also click "Allow network users to change my files" if you're the only person in your network, or if you prefer.
In your MacBook, open the finder and click the "Network" tab in the sidebar. Wait for your Windows computer name to appear/your name and double click it. It will ask for your password, I think the password in your Windows account (I don't know because my MacBook and my Windows have the same password). When you have entered it, you will be allowed to access your Windows hard drive using your Mac... but make sure the Windows computer is turned on.
To share the Mac hard drive to your Windows PC, open System Preferences and click "Sharing" in the Internet and Network section. Check the "Windows File Sharing" in the Services tab. Then click the "Accounts" button to enable the selected users in your network to access your HD. Then below that, there will be a text that says "Windows users can access your computer at (\\IP Address\your short name). Type that address in Windows Explorer from your PC and wait a while. Your Mac is now accessible from your Windows PC. :mac:
Hope I helped.