But where can I find the Myriadcoin-core (is that the Electrum app)? And also where to find the debug console where I propably can find the "importprivkey" ?
https://github.com/myriadteam/myriadcoin/releasesThe core wallet will take a while to sync with the network, maybe a few hours depending on your network connection.
The debug console will be under "Window->Console", then run "help importprivkey" for an explanation.