Hi,

1/ For the menu, you need to create your own menu via Appearance > Menu > create a new menu > add menu items on the left side to your menu > scroll down and check to "Primary Menu" at the bottom.

2/ For sidebar, you can go to Appearance > Widgets > edit the "Main Sidebar" and other sidebar there.

3/ For widgets at the footer, you can manage it via Appearance > Widgets > edit the widgets inside "Footer Column #1", "Footer Column #2", "Footer Column #3"

Best Regards,

PenciDesign