After you successfully set up the connection with Microsoft Entra ID (formerly Azure Active Directory), as the next step, you will need to install Office Add-in to the users in your organization from the Mircosoft AppSource.
Step 1.
Find the Office Add-in section from the Integration tab, click three dots, and click Install Add-in button.
Step 2.
Next, click Install Add-in again.
Step 3.
On the Microsoft AppSource page that opens, click Get it now.
Step 4.
In a new window, please confirm your details to continue, then click Get it now button so you can be automatically redirected to your Microsoft 365 admin center to complete the process.
Step 5.
In a new window, choose the provided options, then click Next.
Is this a test deployment? (Yes or No)
Assign users (Just me, the Entire organization, or Specific users/groups) to specify to whom the add-in is deployed;
Email notification (if you want to send the email notification to assigned users).
Note: Use the Search box to find specific users or groups. If you've deployed to just yourself, you can select Change who has access to add-in to deploy to more users later. Only users with installed Add-in will have signatures applied to emails after deployment.
Step 6.
Please read the app permissions and click Next to proceed.
Step 7.
Click Finish Deployment.
Step 8.
Click Done. After the deployment, you will see the Deployment completed message.
Step 9.
You will be redirected to the Integrated apps tab in the Microsoft 365 admin center Settings, where you will see a green tick near the Newoldstamp Email Signatures app when the add-in is deployed.
Note: If you don't see the app in your Integrated apps, refresh the Microsoft 365 admin center page.
Also, please keep in mind that the Outlook add-ins can usually take up to 24 hours to be processed by Microsoft 365, so the signatures are added. If not, additionally, you can refresh the Outlook client or clear the cache:
1. For Outlook web (OWA) → open your browser and make sure it doesn't cache the old data. Here are the guides on how to do that in different browsers:
How to clear the cache in Chrome
How to clear the cache in Mozilla
2. For Outlook desktop → open your Outlook and follow
this Microsoft article on how to clear the office cache.