On the help page for LibreOffice general you can find instructions that are applicable to all modules, such as working with windows and menus, customising LibreOffice, data sources, Gallery, and drag-and-drop.
If you want help with another module, switch to the help for that module with the combo box in the navigation area.
Enables the display of icon names at the mouse pointer and other Help contents.
Enables the display of a brief description of menus and icons at the mouse pointer.
Some of the shortcut keys may be assigned to your desktop system. Keys that are assigned to the desktop system are not available to LibreOffice. Try to assign different keys either for LibreOffice, in Tools - Customise - Keyboard, or in your desktop system.