There is this feature of the unity dash which was introduced in ubuntu 12.10 and is still there which lets you do these things faster.
Installing an app:
1. Open the unity Dash (windows/Superkey) and select the application scope. Now search for the app you wanna install. You will see the app in the suggestions section. Right Click on it to preview.
preview2. Click on Free Download and you can see the progress bar in the unity launcher itself. Done!
Similarly for removing an installed app:
1. Open the Dash and search for the app you wanna remove.
2. Right click on it and click on uninstall.