On the help page for LibreOffice general you can find instructions that are applicable to all modules, such as working with windows and menus, customizing 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.
Formatting Tables and Cells
Entering Values and Formulas
D'oh! You found a bug (text/scalc/guide/formula_enter.xhp#formula_enter not found).
Database Ranges in Tables
D'oh! You found a bug (text/scalc/guide/database_filter.xhp#database_filter not found).