Added instruction on how to build and run the demo (issue space-ros/d…

…emos#50)

lunar_sim/README.md

@@ -1 +1,63 @@
 # Space ROS Lunar Sim Demo Docker Image
+
+The Space ROS Lunar Sim Demo docker image uses the spaceros docker image (*osrf/space-ros:latest*) as its base image.
+The Dockerfile installs all of the prerequisite system dependencies along with the demo source code, then builds the Space ROS Lunar Sim Demo.
+
+This demo includes a Gazebo simulation of the lunar environment (specfically around the Shackleton crater near the south pole). It uses
+Digital Elevation Models (DEMs) from the Lunar Orbiter Laser Altimeter (LOLA) to accurately simulate the lunar surface in a specific region. It also contains a dynamic model of the Sun that moves according to Ephemeris data.  
+
+## Building the Demo Docker
+
+The demo image builds on top of the `spaceros` image.
+To build the docker image, first ensure the `spaceros` base image is available either by [building it locally](https://github.com/space-ros/space-ros) or pulling it.
+
+Then build `lunar_sim` demo images:
+
+```bash
+cd ../lunar_sim
+./build.sh
+```
+
+## Running the Demo Docker
+
+run the following to allow GUI passthrough:
+```bash
+xhost +local:docker
+```
+
+Then run:
+```bash
+./run.sh
+```
+
+Depending on the host computer, you might need to remove the ```--gpus all``` flag in ```run.sh```, which uses your GPUs.
+
+## Running the Demos
+
+### Curiosity Mars rover demo
+Launch the demo:
+```bash
+source install/setup.bash
+ros2 launch lunarsim_gz_bringup lunarsim_world.launch.py
+```
+
+### Perform Tasks
+
+#### Setup
+
+Open a new terminal and attach to the currently running container:
+
+```bash
+docker exec -it <container-name> bash
+```
+
+Make sure packages are sourced:
+
+```bash
+source ~/spaceros/install/setup.bash
+```
+
+```bash
+source ~/demos_ws/install/setup.bash
+```
+