Which device have you got?
I recently bought a GT-31 and it's not the easiest of gadgets to get your head around so I went to the info and rules section, GPS devices, GT31/GT11, step 2, V 1.4 0315T and followed the well written instructions to update. I found it easier to locate the software by copying and pasting to my desktop. The little toggle switch inside the unit is a little difficult to see (especially with my eyes) and I used a toothpick to switch it over. Once done it was easy enough to get the latest update and the extra font capability makes it easier to read.
Hope this is of some help.