I bought the new macbook pro, can i used the one fcp x to install two machine.

You can legally use FCP X on as many machines as you own (assuming you are not a business!)

Simply copy the FCP X app/icon across to your other machine.

True, but you cannot have both open at the same time.

(Assuming they are on a network)

If it's your personal network it is unlikely that you would want to operate them simultaneously, especially if you had 3 or more Macs . . . you'ld run out of hands. 😉