To install Yak On! 1.27.9 over the air:

Be sure to visit HomeScreen->Options->Yak On! on your BlackBerry after you install Yak On!
If you experience difficulty getting connected, take a moment to review the getting connected document
The user manual is available here

Please read the end user license before installing Yak On!. Installing Yak On! indicates your acceptance of the terms
Yak On!