Update usage-demo3.md

**NOTE:** To view terminal movement on a map, you must first provision maps in AdvantEDGE as described

[here](https://interdigitalinc.github.io/AdvantEDGE/docs/overview/features/gis/#map-provisioning)

##### Demo server

#### Demo server

Demo server is a web server that interacts with the _Application Enablement_ & _Application Mobility_ services

and maintains MEC Application instance state such as:

- Application readiness

- Mobility & termination subscriptions

- Terminal device contexts (counters that continue to increment even with MEC application mobility)

##### Demo frontend

#### Demo frontend

The frontend is an instance-specific dashboard that provides MEC application information.

It provides controls to:

### Obtain demo binaries

##### Build from source

#### Build from source

To build _demo-frontend_ & _demo-server_ from source code:

```

_**NOTE:** Binary files are created in ./bin/ folder_

##### Optionally use pre-built binaries (from GitHub release)

#### Optionally use pre-built binaries (from GitHub release)

```

# Get bin folder tarball from desired release

cd ~/AdvantEDGE/examples/demo3

Therefore, the following steps need to be done prior to running Demo3 application instances.

##### Obtain demo binaries

#### Obtain demo binaries

Use the same procedure described above for Demo3 with AdvantEDGE.

##### Create work directories for each Demo3 MEC application instance

#### Create work directories for each Demo3 MEC application instance

Create work directories of your choice on the system of your choosing; we'll use `~/demo3-mep1` and `~/demo3-mep2` for

this example and create a folder named `static` inside each one of the folders.

notifications sent by the ETSI MEC Sandbox can be received by demo applications. If the system is behind a firewall,

ports will need to be opened._**

##### Copy demo-server to working directories

#### Copy demo-server to working directories

For each application instance, copy the following files to the working directories:

- Server executable (`/AdvantEDGE/examples/demo3/bin/demo-server/demo-server`)

- Template configuration file (`/AdvantEDGE/examples/demo3/demo3-config.yaml`)

               ├── index.html

```

##### Create application instances in the MEC Sandbox

#### Create application instances in the MEC Sandbox

Login via the [ETSI MEC Sandbox](https://try-mec.etsi.org/) frontend.

Deploy either of teh dual-MEP scenarios. Note that the _dual-mep-short-path_ network scenario will trigger

Create two Application Instance IDs called `demo3`, one on _mep1_ and one on _mep2_ respectively.

##### Edit application instance configuration files

#### Edit application instance configuration files

For each application instance, edit the copied template configuration file with instance-specific configuration values.

The resulting configuration should look like this:

port: ''                    # the port number that demo3 is listening on for incoming traffic

```

##### Start Demo3 instances

#### Start Demo3 instances

Start the demo3 instances `./demo3-server demo3-config.yaml` -- after starting the servers, the frontend can be accessed at `<your-ip-address>:<your-port>`

From the frontend, Demo3 can register to MEC011 and then devices present in the scenario can be added.