1. Close app manager and all apps. 2. Open http://wiki.maemo.org/Community_SSU in browser on your N900. 3. Click the green arrow with "Install" written on it (and "Testing" written below) in the top right corner. 4. Hildon Application Manager should open I guess. 5. Accept all it asks you. ("Done" or "Accept" or "Yes"). 6. Wait for it to finish. 7. Close Application Manager. 8. Open applications menu. 9. Find and tap the "Community SSU" icon. 10. Accept all, after finish reboot.