Using the command line interface (CLI) : set
 
set
The set command allows you to set specific properties within a settings category.
Example
To change a default value for a property within the system-administration settings category:
show system admin setting <Enter>
 
config system admin setting <Enter>
setting)# set idle_timeout 2
end
 
show system admin setting <Enter>
config system admin setting
set idle_timeout 2
end