Since this branch is still under development I suggest cloning the repository rather than downloading a zip.
Remember to change your active branch to "attiny1634" after cloning.
- Make sure you have the latest Arduino IDE
- (optional) Install Teensyduino, this will provide some nice extra features (like RAM usage estimates)
- See the readme.txt for upstream instructions to get the general idea of how a core is installed.
- Get a copy of the repo (clone recommended, zip works too)
- Locate/Create the "hardware" directory as in upstream instructions, then copy or link (depending on if you have zipped copy or cloned repo) the repo hardware/tiny and hardware/tools under the sketchbook "hardware" directory.
- Locate/Create "libraries" directory under your Arduino sketchbook, copy/link the libraries from this repo there should you think you need them.
- Update the compiler toolchain in your Arduino IDE, see avr-gcc -directory
- Update avrdude configuration in your Arduino IDE, see avrdude -directory
Remember that the Arduino IDE must not be running when you do this.