Download the current version of Plexus and move it to your webspace. Plexus needs at least PHP5, MySQL4 and mod_rewrite or something similiar enabled.
After moving your plexus to a webspace just navigate to it with your browser. Plexus will ask you for mysql database access data. After that you will be prompted to create the system administration user.
After this two steps you are ready and should see an Error404 page. In the error404 Text click on “create” to start with setting up your frontpage.
If you have any problems with the setup create an issue here on the right.