Setting OPC UA Variables

Hi everyone!
I'm a newbie in the automation field, so please excuse my dumb question.
I am developing an OPC UA server using Node-RED, but I really don't know how to create, read and write variables in it.
I am using the node-red-contrib-opcua library, together with the node-red-contrib-opcua-server that has a precompiled compact server. I can access the OPC UA Server, then that's it.
I am receiving via UDP some variables which I can correctly read, but I also need to make them available on the OPC UA server to make them editable and send them back (again, via UDP).
Can somebody help me on that please?
Thank you so much for your help!