If you log in to netdata cloud you can click on the connect nodes entry at the top of the sidebar, this opens a slide out on the right side of the page where you can select the docker tab, and then copy the three extra params that are shown as new variables in the netdata template
NETDATA_CLAIM_TOKEN
NETDATA_CLAIM_URL
NETDATA_CLAIM_ROOMS
Add these 3 variables as the keys, with the values shown in the cloud UI as the values.
It took a while for the data to show up for me, but it works perfectly for me.