You can't n have them both logged into the ISP at the same time because
a) dsl doesn't work like that
and b) the new router you've ordered doesn't have an ADSL modem built in.
If it's too late to change your order, you'll need to connect the ISP supplied thing to your phone line, turn off wifi etc., and plug your new router into the ISP jobby.
EDITED: 21 Nov 2014 11:56 by KOSWIX