rank aldis viewing eyepiece lens

[kennym]

hello everyone,this is my first range finder camera,bought in minty condition,the lens is clean,the meter works ok,the body is very nice,the only problem is the viewing lens at the back,its not fixed & slides around,how do i fix this,is it glued in position?do i have to take the top off to get at it?or do i just take the front off,can anyone help me with this,
cheers,kenny.