Thanks for your assistance. I tried your config but instead of naming the subnets it just created new object-groups and put the subnets inside them. Please see 'address_lookup.jpg' attached.
I would like to just name the subnets so that when they are looked up in ASDM they have a name. I've also attached a screenshot of the Network Objects page where you can see that the subnets still have no name in the 'Name' column.