How can I use the Elastic-Agent container to collect service logs from another container?

[Gibz]

My target container contains NGINX logs which I wanted to collect from Elastic Fleet's NGINX Integration.

I followed every step, even successfully hosting the fleet server and the agent in two separate containers, what confuses me, is how can I configure my Agent which has the NGINX integration setup on its policy, to collect logs from the service container?

I have mostly encountered examples using the elastic-agent as a package installer directly on the target container.

I've attached three snippets of my docker-compose setup I follow for the Fleet, Agent and App containers.

FLEET SERVER

  fleet:
    image: docker.elastic.co/beats/elastic-agent:$ELASTIC_VERSION
    healthcheck:
      test: "curl -f http://127.0.0.1:8220/api/status | grep HEALTHY 2>&1 >/dev/null"
      retries: 12
      interval: 5s
    hostname: fleet
    container_name: fleet
    restart: always
    user: root
    environment:
    - FLEET_SERVER_ENABLE=1
    - "FLEET_SERVER_ELASTICSEARCH_HOST=https://elasticsearch:9200"
    - FLEET_SERVER_ELASTICSEARCH_USERNAME=elastic
    - FLEET_SERVER_ELASTICSEARCH_PASSWORD=REPLACE1
    - FLEET_SERVER_ELASTICSEARCH_CA=$CERTS_DIR/ca/ca.crt
    - FLEET_SERVER_INSECURE_HTTP=1
    - KIBANA_FLEET_SETUP=1
    - "KIBANA_FLEET_HOST=https://kibana:5601" 
    - KIBANA_FLEET_USERNAME=elastic
    - KIBANA_FLEET_PASSWORD=REPLACE1
    - KIBANA_FLEET_CA=$CERTS_DIR/ca/ca.crt
    - FLEET_ENROLL=1
    ports:
      - 8220:8220
    networks:
      - elastic
    volumes:
       - certs:$CERTS_DIR

Elastic Agent

 agent:
    image: docker.elastic.co/beats/elastic-agent:$ELASTIC_VERSION
    container_name: agent
    hostname: agent
    restart: always
    user: root 
    healthcheck:
      test: "elastic-agent status"
      retries: 90
      interval: 1s
    environment:
      - FLEET_ENROLLMENT_TOKEN=REPLACE2
      - FLEET_ENROLL=1
      - FLEET_URL=http://fleet:8220
      - FLEET_INSECURE=1
      - ELASTICSEARCH_HOSTS='["https://elasticsearch:9200"]'
      - ELASTICSEARCH_USERNAME=elastic
      - ELASTICSEARCH_PASSWORD=REPLACE1
      - ELASTICSEARCH_CA=$CERTS_DIR/ca/ca.crt
      - "STATE_PATH=/usr/share/elastic-agent"
    networks:
      - elastic
    volumes:
       - certs:$CERTS_DIR

App Container (Target:NGINX logs)

  demo-app:
    image: ubuntu:bionic
    container_name: demo-app
    build:
      context: ./docker/
      dockerfile: Dockerfile
    volumes:
      - ./app:/var/www/html/app
      - ./docker/nginx.conf:/etc/nginx/nginx.conf
    ports:
      - target: 90
        published: 9090
        protocol: tcp
        mode: host
    networks:
      - elastic

The ELK stack currently run on version 7.17.0.
If anyone could provide any info on what next needs to be done , It'll be very much helpful, thanks!