assign a button too something thats not assigned on the grip

[tctcb]

hello their,

                  i just wanted too know if you can, how do you assign a button too something in fsx thats not yet been assigned too a button or hat,

when i bought my flight stick  most buttons were assigned already too something (like landing lights ,up/down view ect)how does the two meet(button too item).thanks for listening....