Erase old Time Capsule

I have replaced my Time Capsule. The new Time Capsule has replaced the old one in the Airport network. I hard reset the old Time Capsule. How do I erase the old Time Capsule? I cannot access it in Airport Utility without activating it on the network. The Support article speaks of the "Disk" tab in Airport Utility. NO such tab exists. I am running Yosemite 10.5.5.