Before the Jessie update, I was able to add games using some kind of installer that I could access from the start menu. Now it's gone.
Where can I find these games and apps at SS to download them like I used to?
Here is the information I found about pistore https://www.raspberrypi.org/pi-store-shutdown/
There's a package manager, aka "Add / Remove Software" screen, that you could possibly use as an alternative. It's available in the Menu, under Preferences.
Select (place a check next to) any packages you want to install, click Apply, and enter your password if it prompts you.
It'll show you a progress indicator as it installs.
Then you can find the shortcut under the Menu, assuming the package you installed added one.