To modify a project, use the command gchproject:
gchproject [-A | -I] [-d description] [—addUser(s) [+ | -]user_name [, [+ | -]user_name...]] [—addMachines(s) [+ | -]machine_name [, [+ | -]machine_name...]] [—delUser(s) user_name [,user_name...]] [—delMachines(s) machine_name [,machine_name...]] [—actUser(s) user_name [,user_name...]] [—actMachines(s) machine_name [,machine_name...]] [—deactUser(s) user_name [,user_name...]] [—deactMachines(s) machine_name [,machine_name...]] [—debug] [-? | —help] [—man] [—quiet] [-v | —verbose] {[-p] project_name}