Register the standby server with:

    $ repmgr -f /etc/repmgr.conf standby register
    NOTICE: standby node "node2" (ID: 2) successfully registered

Check the node is registered by executing repmgr cluster show on the standby:

    $ repmgr -f /etc/repmgr.conf cluster show
     ID | Name  | Role    | Status    | Upstream | Location | Connection string
    ----+-------+---------+-----------+----------+----------+--------------------------------------
     1  | node1 | primary | * running |          | default  | host=node1 dbname=repmgr user=repmgr
     2  | node2 | standby |   running | node1    | default  | host=node2 dbname=repmgr user=repmgr

Both nodes are now registered with repmgr and the records have been copied to the standby server.