I've heard that we can use it. Then how can I install it because I dont see it in the Ubuntu Software Center.
Ubuntu – How to download and install Opera in 12.04
12.04operapackage-management
Related Solutions
PPA purge only works if you've installed a PPA (from ppa.launchpad.net). In order to remove it you need to manually remove the line from /etc/apt/sources.list
If a repository is leaving junk around you don't want, you can synaptic and click the Origin button:
Then click on the filter on the left that shows the repository, then you can select them and remove them from there. If you've already removed the repository the packages might be listed under "Local".
As far as to why Opera isn't in the Software Center, people need to tell them to submit it to the Software Center so people don't have to do this kind of thing by hand.
Powertop 2.1, based on the source from the Ubuntu 12.10 version, is available in my bleeding-edge PPA.
To add the PPA and install Powertop 2.1, please open a terminal with Ctrl+Alt+T and type/paste these lines (one at a time):
sudo apt-add-repository ppa:izx/bleeding
sudo apt-get update
sudo apt-get install powertop
Note: If you are unfamiliar with installing third-party software from PPAs, you may want to refer to these questions:
Best Answer
To install Opera, simply go to their download page here. Ubuntu will be auto-detected, and click on the big Download Opera button:
Choose the "Open With" option, and the file will automatically open in Software Center once downloaded:
Click on Install in Software Center, enter your password if asked, and then Opera will be installed: