First, update the app (update was released 12/20). Then, go to the Settings gear on your feed:
In Settings, click on "Additional Services --> Manage":
Then turn all the cool new things to ON:
To use the filters: Take a photo, then SWIPE right to left
There's a couple of Instagram-ish filters, plus overlaps with the speed (wut?), weather, and time.
To make BIG TEXT, tap the big "T" when you're typing:
You can make your keyboard's standard emoji big too:
Don't forget to step up your Snapchat by using the secret extra colors:
Snapchat used to have 3 "secret" filters - b&w, sepia, and negative that you enabled by typing in a codeword, but as of this update, they no longer work. It's okay, these are better anyway. Happy Snapping!