Okay, I got above mentioned download CNEU 2015.10 pc install.rar and a Garmin Nüvi 1490.

The download contains the folowing files in rootfolder:
City Navigator Europe NTU 2015.10.gmap
Disk_32.cab and disk_64.cab
Disk1.cab
CityNavigatorEuropeNTU2015.10update.msi
USB_32.msi and USB_64.msi

So I have been squirrying through the pages on this sight but as I don't know that much of the Garmin lingo I am at a loss about my next step to produce a custom map which I can put on the device.
A lot of possible programs, several of which are outdated. Do I need to unlock, do I need a code, do I need to *****?

I should uncompress the download and install it? Using which .msi?

Then, which program should I use to get my 'own' custom map as a gmapprom.img (or gmapsupp.img)?
Which steps should I take to get it working on the device?
Does it take a lot of work, say for a map of 2 GB?

Hey, maybe I just overlooked the most perfect tut. Might well be. Thanks and regards