Connect to iMac...How?

In order to connect it to another device besides a router the following has to happen, since an IP is required.

1st option:

Set up a DHCP servers on your laptop/desktop. Once you connect the MBL, it will get an IP.

Setback, since it is not connected to your router, all traffic from any other machines will go thru your laptop/desktop. It will also not show up via DNS since it will not register with the router. 

2nd: option: Static IPs for both, the NAS and the laptop/desktop. Simlilar setbacks to above, but a a bit difference since depending on the network selected, you might have to add routes to your router in order to talk to it from other devices

But I will say it again, for the first large transfer, wired both to the router and copy the files. Afterwards, even though wireless is slow, hopefully it will not be large amounts of data as the first time.