To use libreoffice writer type what you wish to type into the main part of the window. If you wish to save your data press the icon that looks like a floppy disk or press control + s. To open a previously saved document press the button that looks like a folder or press control plus o. To load or save a file from the menu file -> open to open a file or file -> save.
How to Launch
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To launch go to menu -> office -> libreoffice writer or run lowriter from the command line.