Put A Paintball Gun On Sand Rail How Do You Put A Butt Plate On A Paintball Gun?

How do you put a butt plate on a paintball gun? - put a paintball gun on sand rail

I have one with my Tippmann 98, and I think they should go to the CO2?
I tried to save, but it's too hard! and move no further.
My friend told me to sand the edges so as to play a little more, but if the sand I can get it, as it was. I do not really buy a new one.