Start the container by typing the following

[rosebaby3892]

Always use  explicit versioning . It may be tempting to use latest or stable when you select an image, but this may result in your application failing to start when you enter docker-compose up next time, due to breaking changes in the newer image that somebody else pushed to docker-hub.
A volume called nexus-data will be mounted at location /nexus-data inside the docker container. The program running inside the container will be able to store its data on the volume.
The port 8081 inside the container will be accessible on port 8081 from the outside world, aka your computer and anybody else on the local network. This allows us to use a browser on port 8081 to administer the running telegram data nexus. You could select any available port for the second (external) port number, but the first number much match the configuration of nexus, which is by default configured to host on 8081.
We expose a range of ports afterwards. These ports are not visible to the outside world, but when we add more docker containers to this compose file, the new containers can communicate with nexus on the exposed ports. The  ports definition is for ports that need to be accessed from outside of docker-compose, the  expose ports are only accessible inside the same docker-compose.
Finally we declare the volume. This is a data storage location that can survive reboots. All data inside a docker container normally gets flushed when the container is stopped. A new container will be created with a clean filesystem as defined in the build process. To let the container persist data, it will need an external data store, and for file systems this is done through a volume.
That's it. We can now start our first container and use the browser to configure it.

Testing
command on the command line:

docker-compose upCopy
The up command tells docker-compose to pull the base images from the internet and to do the initial setup for the containers and volumes.

You will see a log-trace on the terminal about downloading the image layers from docker, followed by the following lines:

Creating network "demo_default" with the default driver
Creating volume "demo_nexus-data" with default driver
Creating demo_nexus_1 ...
Creating demo_nexus_1 ... done
Attaching to demo_nexus_1
nexus_1 | 2017-11-09 09:01:08,901+0000 WARN [FelixStartLevel] *SYSTEM uk.org.lidalia.sysoutslf4j.context.SysOutOverSLF4JInitialiser - Your logging framework class org.ops4j.pax.logging.slf4j.Slf4jLogger is not known - if it needs access to the standard printl
n methods on the console you will need to register it by calling registerLoggingSystemPackage
nexus_1 | 2017-11-09 09:01:08,909+0000 INFO [FelixStartLevel] *SYSTEM uk.org.lidalia.sysoutslf4j.context.SysOutOverSLF4J - Package org.ops4j.pax.logging.slf4j registered; all classes within it or subpackages of it will be allowed to print to System.out and Sy
voice.errCopy
Let it run for a minute, nexus takes some time to setup the data store for first use.

Start up your browser and go to the nexus web page on http://localhost:8081/ It should show you the welcome page.