What am I supposed to write in a format like ''Address Line 1 and 2''?

The first line of your postal address and the second line of your postal address.

But if the second line of your postal address is your town or city check that the next field is not "town/city".

So for example:

Address Line 1: 21, Any Street

Address Line 2: <leave blank>

Town/City: Mytown

or

Address Line 1: Apartment 1234

Address Line 2: 21, Any Street

Town/City: Mytown