The solution to your problem is twofold.

1) you must get to know the architecture of the 8051. That registers and bits/bytes are involved is the nature of the beast. If you do not know how the memory and registers work, then you will not succeed.

2) Using C. As soon as you know what to do with the registers to get your application running, and you have a decent flowchart (or use pseudo-code, whatever you are most comfortable with), you can try and write your program in C. If you master 1) that should not be a major issue.

So If you ask where to start, I would say at the beginning, unless you are fluent in 8051-assembler and know the hardware. (which I doubt, by the nature of your questions...)

So, in short: read about the hardware and how to use it. If done, proceed to flowchart and end-up in C.

hope this helps.

regards
Patrick