Hey, I’ll just put a quick step baby step flashing guide up. 
- The file should be “clockworkos_v0.4.img.bz2” - when you download it, and is 1.67GB.
- First, decompress the compressed file. You should get “clockworkos_v0.4.img” which is 7.95GB.
- To make things easier, download an application to your mac, like Etcher. (It’s what I use) It’s what you use to flash file images to SD cards and USB cards safely. https://www.balena.io/etcher/
- Once you have the program, select the image you decompressed above, ie, clockworkos_v0.4.img
- Insert your SD card into your mac. If should then be selectable under the drive selection dialogue menu.
- Press Flash! If you don’t want to wait afterwards, you can change options in the top right corner to disable “validate write on success” - but if you’re having troubles, it might be best to leave this on.
Hopefully this works! Good luck!!
