The area ID is a feature of an OSPF router interface.
By default, i.e. if you haven't configured otherwise, the area ID 0.0.0.0 (the backbone area) is used.
At Classic devices you have to disable OSPF at the concerned interface and then enabling OSPF again with the correct area ID. OPSF can be configured by CLI.
Following an example with new area ID 1.1.1.1 at interface 1/2:

<login>
<pass>
enable
configure
interface 1/2
no ip ospf
ip ospf areaid 1.1.1.1

Please make sure that all interfaces within one area have the same hello time and dead interval configured.