add reuse guide for existing Azure AI Foundry project

Author: Prasanjeet-Microsoft

docs/DeploymentGuide.md

@@ -124,6 +124,7 @@ When you start the deployment, most parameters will have **default values**, but
 | **Use Local Build**                         | Boolean flag to determine if local container builds should be used.                         | false             |
 | **Image Tag**                               | Image version for deployment (allowed values: `latest`, `dev`, `hotfix`).                   | latest            |
 | **Existing Log Analytics Workspace**        | To reuse an existing Log Analytics Workspace ID instead of creating a new one.              | *(none)*          |
+| **Existing Azure AI Foundry Project**        | To reuse an existing Azure AI Foundry Project ID instead of creating a new one.              | *(none)*          |
 
 
 </details>
@@ -148,6 +149,14 @@ To adjust quota settings, follow these [steps](./AzureGPTQuotaSettings.md).
 
 </details>
 
+<details>
+
+  <summary><b>Reusing an Existing Azure AI Foundry Project</b></summary>
+
+  Guide to get your [Existing Project ID](/docs/re-use-foundry-project.md)
+
+</details>
+
 ### Deploying with AZD
 
 Once you've opened the project in [Codespaces](#github-codespaces), [Dev Containers](#vs-code-dev-containers), or [locally](#local-environment), you can deploy it to Azure by following these steps:

docs/images/re_use_foundry_project/azure_ai_foundry_list.png

@@ -0,0 +1,44 @@
+[← Back to *DEPLOYMENT* guide](/docs/DeploymentGuide.md#deployment-options--steps)
+
+# Reusing an Existing Azure AI Foundry Project
+To configure your environment to use an existing Azure AI Foundry Project, follow these steps:
+---
+### 1. Go to Azure Portal
+Go to https://portal.azure.com
+
+### 2. Search for Azure AI Foundry
+In the search bar at the top, type "Azure AI Foundry" and click on it. Then select the Foundry service instance where your project exists.
+
+![alt text](../docs/images/re_use_foundry_project/azure_ai_foundry_list.png)
+
+### 3. Navigate to Projects under Resource Management
+On the left sidebar of the Foundry service blade:
+
+- Expand the Resource Management section
+- Click on Projects (this refers to the active Foundry project tied to the service)
+
+### 4. Click on the Project
+From the Projects view: Click on the project name to open its details
+
+    Note: You will see only one project listed here, as each Foundry service maps to a single project in this accelerator
+
+![alt text](../docs/images/re_use_foundry_project/navigate_to_projects.png)
+
+### 5. Copy Resource ID
+In the left-hand menu of the project blade: 
+
+- Click on Properties under Resource Management
+- Locate the Resource ID field
+- Click on the copy icon next to the Resource ID value
+
+![alt text](../docs/images/re_use_foundry_project/project_resource_id.png)
+
+### 6. Set the Foundry Project Resource ID in Your Environment
+Run the following command in your terminal
+```bash
+azd env set AZURE_ENV_FOUNDRY_PROJECT_ID '<Existing Foundry Project Resource ID>'
+```
+Replace `<Existing Foundry Project Resource ID>` with the value obtained from Step 5.
+
+### 7. Continue Deployment
+Proceed with the next steps in the [deployment guide](/docs/DeploymentGuide.md#deployment-options--steps).