Here is a good thread: Guide: how to flash ATtiny13a based drivers (NANJG, QLITE, etc.) with custom firmware
I made a post in another thread after flashing my first driver (photo link is broken): what programmer to buy - #10 by Mike_C
Here is some info on fuses: AVR Tutorial - Fuses
Here is a fuse calculator for the old MCUs like 13a, 25 and 85: AVR® Fuse Calculator – The Engbedded Blog