There are 2 ways to do this

There may be times when you need to look at a list of packages that were recently installed in Ubuntu for troubleshooting purposes or perhaps just to find a program you installed that isn’t showing up in the menu. There are two ways to find out what was recently installed. You can view recently installed packages by date using the Synaptic Package Manager and from the command prompt using a Terminal window.

To view recently installed software packages using Synaptic Package Manager, select Administration | Synaptic Package Manager from the System menu.

In the Synaptic Package Manager dialog box, select History from the File menu.