No Serial input node

Warning: totally newbie
Hello,
I just installed Hassio on rp3 and added Node-Red from the community repository,
in order to read rflink gateway data from the serial port.
The problem is that there is no serial input node.
How can I add serial support?
Thanks,
Wim

Continue:
Found node-red-node-serialport on the palette, but it failed to install.
I tried npm i node-red-node-serialport before but that also failed.
It said: -bash: npm: command not found
Please help!
Wim