Map installation-XXL

IanMeyers Registered Users Posts: 1
New Traveler
edited January 2019 in Devices using TomTom HOME
My device is full with maps of Australia and USA and I have copied these to my computer. I am about to buy maps of Europe so what is the procedure for installing these new maps and not losing the existing ones. Also how do I select only parts of the maps to install.
Is there an online manual to guide me through all of this.