The developers of Mer implemented an installer, which leads through all the steps of installation. In order to use the installer you need to open: install file with your device, which will prompt you to install the file (about 2.5MB) and add the Extras, Extras-devel and tspre.org repositories if they were not added already.
After the download and the installation go to Settings -> Application Manager -> Utilities -> Browse Installable Applications -> Other and system and you will find a program “Install Boot-menu” and “Merinstaller”. If you did not install those by pressing “OK” before, do it now.
The Simple Install will create a boot-menu entry for you. However, for more advanced installations - if you already have multiple booting OSes – you might want to read about its configuration – you may need to make a .item if you have a clone-to-SD copy of Maemo or Deblet. You can also find out how to change the default boot menu item and other boot-menu tricks.
Assuming you created all the .item files you wanted, go ahead, and start the boot-menu installer from Utilities -> Install Boot-menu. Its advised to close all other applications and network connections, but the installer will tell you all relevant information.
Are you sure to continue? – yes
Create backup of current initfs – yes/no
Remove unneeded extra (and factory testing) stuff? – yes
install telnet server for network recovery? – yes
install dropbear ssh server for advanced network recovery? – yes
/etc/bootmenu.conf found, do you want to add it to initfs? – yes
Ready for flashing this image? – yes
After a successful flash, the device will reboot and you should see the boot-menu, where you can select the partition you want to boot. Choose the operating system where you just installed the installer for Mer and boot it.
Now start the Merinstaller via Utilities -> Install Mer. Follow the instructions. When prompted for the URL= you can point it to any rootfs image you want.
Once the installer puts the extracted rootfs to your device you can reboot and chose the partition where you put Mer.
