there are more than one dell adamo xps models on the market
since dell has a pretty good database with a lot of guides online - i can only suggest that you go to http://support.euro.dell.com/ and search for wwan and your exatc model - you will find a step-by-step guide to install the wwan card.
and one thing - if something goes wrong with the driver installations - check the hardware id's - it would not be the first time that dell send out the wrong card!