LibreOffice is is one of so called "downloadable extensions" (i.e. optional software in 4MLinux, which is installed in the /opt directory by default).
1) Choose LibreOffice from the Extensions menu:
2) You must confirm the installation:
3) Now 4MLinux will download and install the newest LibreOffice for you:
LibreOffice suite integrates with the rest of the 4MLinux desktop, meaning that you will be able to open your documents with any of the following file managers: Midnight Commander, Path Finder, and X File Explorer.