We've written a full graphics library specifically for this display which will get you up and running quickly. The code is written in C/C++ for Arduino but is easy to port to any microcontroller by rewritting the low level pin access functions.
The TFT LCD library is based off of the Adafruit GFX graphics core library. GFX has many ready to go functions that should help you start out with your project. It's not exhaustive and we'll try to update it if we find a really useful function. Right now it supports pixels, lines, rectangles, circles, round-rects, triangles and printing text as well as rotation.
Two libraries need to be downloaded and installed: first is the ST7735 library (this contains the low-level code specific to this device), and second is the Adafruit GFX Library (which handles graphics operations common to many displays we carry). You can install these with the Arduino library manager.
Open up the Arduino library manager:
Search for the Adafruit ST7735 library and install it
Search for the Adafruit GFX library and install it