If you docker registry is private and self hosted you should do the following :
docker login <REGISTRY_HOST>:<REGISTRY_PORT>
docker tag <IMAGE_ID> <REGISTRY_HOST>:<REGISTRY_PORT>/<APPNAME>:<APPVERSION>
docker push <REGISTRY_HOST>:<REGISTRY_PORT>/<APPNAME>:<APPVERSION>
Example :
docker login repo.company.com:3456
docker tag 19fcc4aa71ba repo.company.com:3456/myapp:0.1
docker push repo.company.com:3456/myapp:0.1