How can I run two docker containers in the same network namespace?

I want to run two docker containers in the same Linux network namespace.
My goal is to route all my torrent traffic through OpenVPN.
This script successfully creates a openvpn client container.
I can successfully enter this namespace and verify my IP address is indeed the OpenVPN IP address.

My issue is – How do I run the qbittorent docker container inside the openvpn network namespace?

Is there some sort of flag when starting a docker container to specify the network namespace to run in?
Any other possible solutions?
It is my understanding that I can not change the network namespace of a an already running process
Thanks

UPDATE
SOLUTION
add this
–net=container:$openvpn_client

openvpn_client="openvpn-client"
torrent_client="torrent_client"
dewinettorrent_ns="dewinettorrent_ns"

function getpid {
        pid="$(docker inspect -f '{{.State.Pid}}' "$1")"
        echo $pid
}

docker rm -f $openvpn_client
docker rm -f $torrent_client
ip netns delete $dewinettorrent

ip netns pids $dewinettorrent_ns | xargs -t kill -9

docker run -d  \
  --privileged \
  --name=$openvpn_client \
  --volume /home/dewi/code/dot-files/vpn/:/data/vpn \
  --volume /home/dewi/code/dewi_projects/ivacy_vpn_auth:/data/vpn/auth-user-pass \
  docker-openvpn-client-dewi


docker run  -d \
  --name=$torrent_client \
  -e PUID=1000 \
  -e PGID=1000 \
  -e TZ=Europe/London \
  -e WEBUI_PORT=8080 \
  -p 9080:8080 \
  -v /path/to/appdata/config:/config \
  -v /path/to/downloads:/downloads \
  lscr.io/linuxserver/qbittorrent

mkdir -p /var/run/netns;
ln -fs "/proc/$(getpid $openvpn_client)/ns/net" /var/run/netns/$dewinettorrent_ns

mkdir -p /etc/netns/$dewinettorrent_ns/
echo 'nameserver 8.8.8.8' > /etc/netns/$dewinettorrent_ns/resolv.conf

docker exec -i $openvpn_client bash /data/scripts/entry.sh &

ip netns exec $dewinettorrent_ns curl icanhazip.com #successfully returns back my VPN IP address

Answer

docker run ... --name app1 image1
docker run ... --net container:app1 --name app2 image2

$ docker run --rm -d --name nginx nginx
351aa6f8dbfd46600bb6e7466e49fa1a62bc9d41e3c3001b4f1f55bce33a4720

$ docker run -it --rm --net container:nginx nicolaka/netshoot bash
bash-5.1# ss -lnt
State                    Recv-Q                   Send-Q                                     Local Address:Port                                      Peer Address:Port                   Process                   
LISTEN                   0                        511                                              0.0.0.0:80                                             0.0.0.0:*                                                
LISTEN                   0                        511                                                 [::]:80                                                [::]:*                                                
bash-5.1# exit
exit

Attribution
Source : Link , Question Author : dewijones92 , Answer Author : BMitch