You can use the .org directive to specify an actual address to locate the data at. Also, you may want a separate label for each character. Something like ...
and so on.
Then, to access the character data, load the symbol that specifies the character data that you want into your pointer register, and access it via the pointer with the LPM command. Read up on LPM ... the address you want must be modified slightly to work with it. I think it requires a shift, but I don't remember which direction.