1
Click on the Ubuntu Software Center icon. This icon located on the launcher bar at the left hand side of the screen.

2
Type in "flashplugin-installer" on the search bar and press enter.

3
You should find the Adobe Flash plugin pop up in the search results.

4
Click on the "Install" button.

5
After installing, try opening a web browser and going to a website that requires Flash.

6
If it works, you have successfully installed Adobe Flash Player. If not, repeat the steps carefully.

Hope this helps.
Enjoy! - Nasty