You probably install apps from the ubuntu software center, so you first got to open it and then search for the app and then install, and similarly do the same for removing/uninstalling them. You can use the terminal to get these things done faster but for that you need to know the exact package name to install/remove.
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.