Click on the menu button in the bottom left corner and select Control Center. Find the button labeled Update Manager and click on it and then enter your password that you gave while installing earlier.
If the next screen appears empty, click on the Refresh button at the top and then click on Install Updates.
You'll also be able to find this in the bottom right corner of your desktop and you'll know you have an update if you have a blue indicator on the shield, but I just wanted you to be able to find it.
The second method for installing the updates is through terminal. You can access terminal by clicking on Menu in the bottom left corner, selecting terminal and typing the following commands:
sudo apt-get update
sudo apt-get upgrade
When prompted with Do you want to continue [Y/n]? press Y, and the updates will begin downloading. Your system is now up to date.