This command can only be used by root
Solution 1:
You need to change your wget command from:
wget -O - http://debian.neo4j.org/neotechnology.gpg.key | apt-key add -
to:
wget -O - http://debian.neo4j.org/neotechnology.gpg.key | sudo apt-key add -
Solution 2:
The error message is from apt-key, and as it says, use it with sudo:
wget -O - http://debian.neo4j.org/neotechnology.gpg.key | sudo apt-key add -