Recently, my built-in airport in my macbook (about 3 years old) is not working well, the signal received is low. Probably due to it's age. So I bought a D-link Wireless Adapter for my network access.

However, making the adapter works in my mac is not as easy as in the windows environment. But don't worry, it's not that difficult to make it works. With the help of the Google, I found that there is a manufacturer worked an interface and driver for connecting the wireless in Mac Environment. Here is the link to the manufacturer. http://www.ralinktech.com/ralink/Home/Support/Macintosh.html
Download the USB (RT2870/RT2779/RT307X) if you are also using D-link DWA-140, (dont know if the others work, but worth trying). Install the pkg after you download and extract.

After successful installed and restarted your mac, you can plug in your USB adapter and the software installed will initiate and you can connect to your wifi network now.

And finally one more important step is required before you can connect through this new network interface, you have to update your network location. Go to System Preferences, then go to Network section, it will automatically update the network interface by adding this newly installed interface (This section is a little bit annoying with not stop pop-up, dont know why, just wait about 10 sec.). After it successfully installed (you will see a new green dot), you will be able to turn off your airport adapter and use this USB to connect to the internet.

Here is the screen cap for the installed software: