If using a pc, if express no longer has the option to install to card, do it via basecamp. firstly download latest maps to your pc using express, once done open base camp and connect your nav, ensure your nav and pc can see the sd card (it can ) good, now go to maps heading at the top of of your base camp window left click and highlight or tick next to your latest map version, once you have done that look down the list a little bit and you will see install maps select that, you should see the map install window open, select your card from the list (you may need to use the drop down arrow to find it).
Once selceted use your mouse to highlight the whole area you need ande then choose continue and then next window choose proceed.
NOTE if the card is not visible none of the above will work.