You can attack these, provided they are not shielded,but you cannot capture them. You only have one town per account .
Do you still need more information? That is do you need to know how to attack them?
You have to be a new player and you must have been through the tutorial, the simple answer is you attack other towns like they showed you how to attack resource locations.
You can find something to attack using the watch tower, or just by looking on the global map, if you click on the object it should come up with the options avaiable, one of which is attack , click on this and it should then allow you to form a body of troops for a march.Then just hit send.
Beware that some of these dead towns or towns of people who are still playing, could be stronger than you and you can potentially loose.
Scouts sent first give you the chance of seeing what's there, but if you scout a live town they will know that you have done this if they have at least one scout themselves.