Changing Concrete Density in STAAD.Pro


I want to amend the density of concrete but I am at a loss of how to do so. The density within my file is currently around 24kN/m3 but I want to amend this to 25kN/m3 to be inline with Eurocode 1991. I have attempted to use the 'Density' command under 'Commands > Material Constants' but I get the following window when I try to input a value for 'the view' which is a large concrete slab.

Any help would be greatly appreciated.