Each instance will be an assembly, e.g. if generic is FRUIT.ASM, the instances will be APPLE_INST.ASM, PEAR_INST.ASM etc.
It's useful to add the "_INST" to the instance label for 'housekeeping' purposes.
Add a string parameter say 'FRUIT_SELECT', this string will hold the selection of the NAME of the instance you want to show in the main assembly, e.g. APPLE, PEAR etc.
You can enter this through Javascript on a web page or Java or manually.
Add the family table to the main assembly
In Proprogram for the main assembly, in RELATIONS, add
COMP_FRUIT = FRUIT_SELECT+"_INST.ASM"
Now find in the EXECUTE section the entry for the FRUIT.ASM
ADD SUBASSEMBLY FRUIT
INTERNAL COMPONENT ID 12527
PARENTS = 36(#1)
END ADD
and modify this to read
ADD SUBASSEMBLY (COMP_FRUIT)
INTERNAL COMPONENT ID 12527
PARENTS = 36(#1)
END ADD
(You could also add here some logic which switches this OFF)
e.g.
IF (FRUIT_REQ=="Y")
ADD SUBASSEMBLY (COMP_FRUIT)
INTERNAL COMPONENT ID 12527
PARENTS = 36(#1)
END ADD
END IF
where FRUIT_REQ is a parameter you have set to either Y or N
Now save the edit, and regen the main assembly to show the selection you made.
Good luck