Is there a way to assign a WAN address to octopi?
What do you mean by a WAN address (A wide area network is usually an extended private network used by business, governments, schools etc, so checking your meaning)? Do you mean a fixed/static IP address on your local network (assume not), or do you mean a Public IP address (i.e. the Internet) ? Or something else?
Either way, Octopi is just a raspberry pi running a flavour of Linux,, so all done in a similar way.