There are two ways to create a new Calc document:
From Scratch. To create a new empty document, click File › New › Spreadsheet.
From a Template. To use a template, click File › New › Templates and set the Filter to Spreadsheets. Choose a template from the list and proceed with Open. Note that by default, LibreOffice does not ship with predefined templates for Calc.
Access the individual sheets by clicking their respective tabs at the bottom of the window.
Enter data in the cells as desired. To adjust the appearance, either use the Formatting toolbar or side bar panel, or use the Format menu—or define styles as described in Section 11.2, “Using Formatting and Styles in Calc”. Use the File menu or the relevant buttons in the toolbar to print and save your document.