To start LibreOffice, click Applications › Office › LibreOffice. In the LibreOffice start center, choose the type of document you want to create.
There are multiple methods to directly start one of the LibreOffice modules:
If any LibreOffice module is open, you can start any of the other modules by clicking File › New in the LibreOffice module and then selecting the type of document you want to create.
To start individual LibreOffice modules open the Activities Overview by pressing Meta and search for libre.
As an alternative, use the command libreoffice and one of the options --writer, --calc, --impress, --draw, or --base to start the respective module.
LibreOffice has many command line options, especially for allowing document conversions. To learn more about the command line options of LibreOffice, see libreoffice --help or the man page of LibreOffice (man libreoffice(1)).
Before you start working with LibreOffice, you may be interested in changing some options from the preferences dialog. Click Tools › Options to open it. The most important ones are:
LibreOffice › User Data
Specify your user data such as company, first and last name, street, city, and other useful information. This data has many uses: It is used in the comment functions of Writer and Calc, for authorship information in PDF documents, and for serial letters in Writer.
LibreOffice › Fonts
Map font names to installed fonts. This can be useful if you exchange documents with others and the document you received contains fonts that are not available on your system.
Load/Save › General
Contains loading and saving specific options. For example, you can choose whether to always create a backup copy and which file format LibreOffice should use by default.