If you want to access any of the C variables from assembly then you have to use "_" in front of their name. For accessing any array you can use indexed addressing mode, here is an example for the same.
For accessing an array from assembly, X will point to the index.
RAM_SETPAGE_IDX >_MyBufferName ; This instruction is required when your device have more than one page of RAM and paging is enabled.
mov A, [X + _MyBufferName]
inc / dec X