Like on windows you don’t get any software package to install the UTL RUIM holder for connecting to the internet. The thing you have to do on Linux is that, at first check whether the Wvdial package is installed on your Ubuntu or not. If this package is absent download this package and install this package. Then  just you have to do is following..

At first to check whether your device is detected by the system or not  write this in terminal
$ ls /dev/ttyUSB*
If your result is /dev/ttyUSB0 than proceed further otherwise unplug your modem and try again or you may have to restart.
Once the modem is detected write the following command in terminal
$ gksudo gedit /etc/wvdial.conf

and than paste the following

[Dialer Defaults]
Modem = /dev/ttyUSB0
Baud = 230400
Init1 = ATE0
Init3 = AT+CTA=0
Init4 = ATEOV1
Init5 = AT
Init6 = ATS0=0
ISDN = 0
Modem Type = Analog Modem
Phone = #777
Username =
Password = your number
Stupid Mode = 1
New PPPD = yes

Save the file and than close the window.

Now dial using the following command
$ sudo wvdial
Now wait for about 30 seconds and you should be surfing the net.

And remember you may have to dial 5/6 times in the terminal  before you have a internet connection. Now  you can enjoy the internet connection on your computer.