Please feel free to try the Colibri Demo.
Using your local LibreOffice / OpenOffice you can connect to the OLAP server with the OLAP Plugin using this connection configuration (OLAP->Modeller->New Connection):
Please be aware that the demo instance is reset every night and thus your changes are not persistent. Please also keep in mind that the demo is open for public, so everybody will be able to see your uploaded data.
Do not forget to export your project, if you want to keep it.