It works like this:
You can call the country where you are and Canada at the regular cost (which, if you have unlimited minutes, means for free).
Same applies for receiving calls: you can be called from anywhere in the world at your regular per minute fee (presuming you have unlimited minutes, for free).
The ones who call you just pays the regular fee because your number doesn’t change - it would hardly be fair for them to be exposed to a sudden higher fee because they weren’t aware you were abroad :)
However you can’t call OTHER countries, even in Europe for free, those would be seen as calling abroad and you’d pay the regular fee to call from Canada to that country.
Oh as for your question about how to call: just dial any number as + (country code) (area code) (number)… that should work. If you call Canada, it would be +1 xxx xxx xxxx
However, if you call some countries like The Netherlands, you might need to leave off the zero in the area code. For example a number like 012 3456789, you’d need to dial the number as +31 12 345689.
See also https://www.koodomobile.com/en/help/easy-roam
