As I said in chat, there are a lot of languages to program the 8051 in. Assembly, C, and BASIC are the most popular. For programing in Assembly,
**broken link removed** is a link to a site that has the instruction set for 8051 assembly. For programing in BASIC, it really comes down to the compiler you use, each one is a bit different. Programing in C would most likely be the fastest way, but I won't be able to help you with that.
As for getting the software onto the device, you have to force the controller into program mode. In that PDF I gave you it talked about how to do this software wise. Hardware wise, try looking
here.