Install then add it to collectd.conf (default values shown and may be omitted):

<LoadPlugin python>
  Globals true
</LoadPlugin>

<Plugin python>
    LogTraces true
    Import "write_influxdb"

    <Module "write_influxdb">
        host "localhost"
        port 8086
        username "root"
        password "root"
        database "collectd"
        ssl false
        verify_ssl false
        use_udp false
        udp_port 4444
        retry false
        buffer false
    </Module>
</Plugin>

In addition timeout can be specified as an integer to set the HTTP timeout for writing to InfluxDB. Additional types.db files can be specified by adding one or more typesdb paramaters to the module config specifying the path to the file. Write buffering to InfluxDB can be enabled by specifying buffer true in the config. By default it will flush the buffer every 1024 values or 10 seconds (whichever happens first). The format to change these is buffer true 2048 to increase the value buffer or buffer true 1024 5 to change the time buffer.