We have example code ready to go for use with these TFTs. It's written for Arduino, which should be portable to any microcontroller by adapting the C++ source.

Two libraries need to be downloaded and installed: the TFTLCD library and the GFX library. You can install these libraries through the Arduino library manager.

Open up the Arduino library manager:

Search for the Adafruit GFX library and install it

Search for the Adafruit TFTLCD library and install it

If using an older version of the Arduino IDE (pre-1.8.10), also locate and install the Adafruit_BusIO library (newer versions do this automatically when using the Arduino Library Manager).

We also have a great tutorial on Arduino library installation at:
http://learn.adafruit.com/adafruit-all-about-arduino-libraries-install-use

In the TFTLCD Library folder, you will need to edit TFTLCD.h. On about line 12, you will see "#define USE_ADAFRUIT_SHIELD_PINOUT". Comment out this line and save the file.

After restarting the Arduino software, you should see a new example folder called Adafruit_TFTLCD and inside, an example called graphicstest. Upload that sketch to your Arduino. You may need to press the Reset button to reset the arduino and TFT. You should see a collection of graphical tests draw out on the TFT.

Now you know everything is working. If you're having problems, check the serial port monitor. The first thing the sketch does is read the driver code from the TFT. It should be 0x9328 or 0x9325 so if you see something like 0x8328 that means that the D8 pin is not wired correctly and if you get 0x9228 then pin D0 is not wired correctly. Remember that the two bytes are read one after another.