Wires are always better, so if you can do it without it being a mess running along the floor (unless you're ok with that?), then wires are the way to go. Else, wireless.
Whichever you decide to use, you will initially need to set the modem/router up using a wired connection.
Having done this successfully, you can then connect through wirelessly which is the reason for buying this model.
If you had intended using a completely wired system then we would have recommended an alternative cheaper router
Sorry - I didn't explain better - I have a Main PC and a couple of laptops (wireless)
I just wondered about the length of cable that I could use between the Router and main PC (Should I place the router downstairs where the phone socket is or should I place it closer to the PC (upstairs) ?)