where to get

I don't know any app by that name, but I suspect you mean Active Sync? To hook your phone up to the pc and synchronize it?

Your phone already has it built in. Depending on which OS you're running on your PC, you can download the appropriate file from Microsoft.com.

If you're running XP, you'll need ActiveSync 4.5 : http://www.microsoft.com/windowsmobile/en-us/help/synchronize/ActiveSync-download.mspx

If you're running Vista, you'll need Windows Mobile Device Center 6.1:
http://www.microsoft.com/windowsmobile/en-us/help/synchronize/device-center-download.mspx

Make sure you'll know if you're running 32-bit or 64-bit if you have Vista.

it should work pretty easy:
connect your phone to the computer via usb. A window should pop up on your phone asking you if you want to connect to ActiveSync or Ext. Hard drive. Pick ActiveSync.

Then your pc should initialize the sync program.