If you want to write one byte to a memory location, then you must obviously declara a pointer of the type: "pointer to single byte".

The compiler manual should tell you what data types there is that is a single byte large.
The standard C language reference should tell you how to go ahead and create a pointer to such data type.
The compiler manual should tell you if you need to augment the declaration with compiler-specific keywords becaues the address is located in specific memory (code, xdata, ...) that requires that specific addressing instructions are selected by the compiler.

Have you looked at the compiler manual?

Have you looked at the example code that is normally supplied with a compiler or with a development board?

If you know A and you know B, then you should be able to figure out what C is in A + B = C. Programming is to a large part to take many simple facts from different places and use as building blocks to create more complex constructs. And then to continue to use these constructs to build even more complex constructs.

But programming is something the programmer must do - not something that can be left to a web forum.

We can help if you find a sentence somewhere in a manual that you do not understand how to "decode". But you must work on combining multiple facts into a big picture relevant to your specific problem.