在ubuntu 18.04中电源图标旁边显示设置图标,但我无法访问

in my operating system ,i often found wifi hardware disable problem .that's why downloaded wicd and installed it ,and then i fixed that problem.but after installing that i cannot access my setting.i command in alt+f2 gnome-control-center but it showed 'command not found' and i search in menu option 'setting' but here also i get nothing.i tried to reinsall gnome control center again but in 60% it prints errorenter image description here