How do I actually code this?

http://elm-chan.org/works/sd8p/report.html

I want to make one of these, can I use the Uno as the programmer (as I usually do) or do I need to use something else?

I think I can suffice with a mono version for now.
Here is the quote:

"The Mono configuration uses five I/O pins and it does not need to switch RSTDISBL fuse. It can be programmed in ISP method that supported by all AVR programmers. The dual output configurations, Stereo, Hi-Res and OCL, use all I/O pins including RESET pin. There is a problem that high voltage serial programming method is required to switch the RSTDISBL fuse. But most AVR programmer does not support the HVSP method. The ISP method can also program the RSTDISBL fuse only the first time but cannot re-program."

Are you asking how to code (as the title tells), or are you really asking how to program the chip ?
That's a big difference.

If the question is about HVSP, you'd need additional hardware.
Programming that way requires putting a 12 volt level to the /reset pin, and your Arduino can't do that without a little help.
In normal use the /reset pin is at the 5 volt level.
A reset is forced by pulling it to GND level.
And in this case putting 12 volt to it will have it enter programming mode.

This is only valid for certain chips, you will do serious damage if you try this on chips that do not support it.

Download the HEX
Use ArduinoISP on your UNO or Nick Gammon's programmer to program the tiny85

Ray

You can program the mono version with your Arduino.

As long as you don't use more than 5 I/O pins, you don't need to worry about that high voltage programming stuff.

mrburnette:
Download the HEX
Use ArduinoISP on your UNO or Nick Gammon's programmer to program the tiny85

Ray

Thanks! Exactly what i was after. The downloaded zip contains many c files. Do I extract these in to a new library folder in my arduino directory? Is main.c the one I would need to write to the attiny85?

The zip has precompiled hex files which you can program on to the chip.