Install Logstash Plugin in sebp/elk for Docker

[Sharivari]

Hi there,

I'm using ELK (sebp/elk) for Docker on Windows, so im using the virtual machine.
Inside the VM i am installing elk via:

sudo docker pull sebp/elk

and

$ sudo docker run -p 5601:5601 -p 9200:9200 -p 5044:5044 -it --name elk sebp/elk

Now I want to install a plugin for logstash, this one:

logstash-plugins/logstash-input-http_poller

In the documentation it says, I should use this command:

FROM sebp/elk

WORKDIR ${LOGSTASH_HOME}
RUN gosu logstash bin/logstash-plugin install logstash-input-rss

Problems:

1. My LOGSTASH_HOME folder doesnt exist in the VM
2. The Logstash Plugin file doesnt exists in the bin folder
3. The command gosu is not found.

What am I doing wrong and what should I do? Please help