Firstly need to install "Blueman"

simply go to Terminal by Applications > Accessories > Terminal

type or copy the code below to the terminal <Enter> and input the Password then wait for a while

sudo apt-get install blueman

Only for UBuntu 9.10  there would be a little bit additional setting

go to System > Administration > Software Source

Type in box the below command

ppa:network-manager/trunk

then click Add Source

Click Close button to close the Software Source page

then there would be another window pop up to ask "The information about available software is out-of-date"

then Press Reload

Click on Install Update button,

wait until finish and Restart the computor.

To using the Blueman at the first time

- Open bluetooth in your mobile phone.

- Click Bluetooth icon at task bar (Top-right of the screen)

- Find the bluetooth device

- Right-Click at the Device you desire to connect to the internet

-  Choose Serial Ports > Dialup Service