The the MeeGo preview for the N900 first came out, in order to install it you need to make your own image and then flash it onto the N900. Things have moved along since then and a ready to flash MeeGo image is now available from Nokia’s own servers. So if you have been wanting to install MeeGo on the N900 but have been waiting for it to become just a little easier, the necessary guides are here.
But before you embark on the MeeGo journey with your N900, please keep in mind that this is still very much a developmental release and that it holds no value for an everyday users and if you think you fall under that category, its better to hold off. There also some issues with backlighting, which are being discussed here.