You'll need a few libraries to use this FeatherWing!
We have example code ready to go for use with these TFTs.
From within the Arduino IDE, open up the Library Manager...
Search for ILI9341 and install the Adafruit ILI9341 library that pops up!
Next up, search for Adafruit GFX and locate the core library. A lot of libraries may pop up because we reference it in the description so just make sure you see Adafruit GFX Library in bold at the top.
If using an earlier version of the Arduino IDE (pre-1.8.10), locate and install Adafruit_BusIO (newer versions handle this prerequisite automatically).
Repeat the search and install steps for the Adafruit_ImageReader library.
After installing these libraries, you should see a new example folder called Adafruit_ILI9341 and inside, an example called graphicstest_featherwing.
Upload that sketch to your Feather. You should see a collection of graphical tests draw out on the TFT.
If you're having difficulties, check the serial console.The first thing the sketch does is read the driver configuration from the TFT, you should see the same numbers as below. That will help you determine if the TFT is found, if not, check your Feather soldering!
Once you've got the demo working, check out the detailed documentation over at http://learn.adafruit.com/adafruit-gfx-graphics-library for more information on how to use the GFX library to draw whatever you like!