If you're wanting to know general claiming command, click here.
First, while holding your golden shovel in your hand, you put the shovel into subdivision mode with the command /subdivideclaim.
To create the subdivision: Right click the shovel at one corner of the area you wish to subdivide, and again at the opposite corner (as if you were making a new claim around it, note that subdividing a claim does not use any additional claim blocks) You will then see the area outlined in wool and iron blocks.
To remove the subdivision: Stand inside the sub-claim and type /abandonbandonclaim as normal. You can't remove the larger main claim when it's subdivided with the /abandonclaim command. If you want to delete the main claim the command changes to /abandontoplevelclaim which deletes the main claim and all subdivisions.
For a basic tutorial on how to claim, you can watch this video: