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. To have save your file as a pdf press the button that is a sheet of paper with curved red lines on it or go file -> export and select the file type as pdf.
After you are done writing your document you can press the button that looks like a printer to print, press control+ p or file -> print.
