The first adress is the one of the main sprite, all sprites must be of the same dimentions, type the adresses without the .bmp, sprite groups are used to prevent incompatible 
attachables from overlapping, for example if you have two scopes, they should be in the same group. Groups are named with a single ascii character. This also contains an example:
In this example smg is the mains sprite(first adress), a,aa,b,c are attachable sprites, a and aa being in the same group, and ss000 to ss011 are the output, note that the grey background has
been replaced by 255 0 255 pink. PM me if you need any help.

Also adresses can be relative or absolute: if the .exe is in C:\whatever\ and you want the .bmp called image that is also in that folder you can write either his:
C:\whatever\image
(absolute) or this:
image
(relative)