If you own a dedicated device, then you will need to download the files to a computer and then transfer them to your device, before locating each one on the device on the required day; if you are unsure of how to do this, you will need to refer to a user manual for the device. You may also need to consider downloading and/or purchasing
digital mapping; there are some country-specific websites, but a few sites offer global or Europe-wide mapping, including
https://garmin.opentopomap.org/ (Garmin-specific, but free) and
https://www.outdooractive.com/en/ (mapping available for an annual membership fee).