How do I share my Internet connection wirelessly while using it on my MacBook Pro?
I've used  Idea Netsetter Dongle and shared my internet over the Wifi. 

 


First connect to the Internet with Idea Netsetter 3G 
Open System Preferences > Sharing

Select the Network which you want to share ( In your case it's Ethernet Adaptor )
Select the network(s) which you want to share the internet to (In your case Wifi)

Don't forget to switch you're Wifi On

Now if you look at the Wifi Icon on your Menu Bar , You'll notice something different.





Now take any other device ( iPhone , Android Phone , iPad ) and connect to your WiFi Network.


Hope this is what you were looking for !