In order to embed your Halo portal in Teams, you will need to create a Microsoft Teams app for it. There are a few steps needed to do this which will be detailed in order below.
Azure AD App:
Firstly, you will need to set up an App Registration in Azure Active Directory. This can be done by navigating to the App Registrations tab of Azure AD and selecting new registration. The only thing you will need to set up here is the access type and name, no redirect URI's are necessary. Once this registration is complete you should keep this window open as you will need to refer back to the Application ID when setting up your Teams application.
After setting up the Azure AD application go to dev.teams.microsoft.org and log in with Azure AD, once you have access to the portal select the Apps tab and create a new app:
After creating the App you will be taken to the basic information page, fill in the mandatory fields with the relevant details for your organisation. These fields must be filled out for this to work. Once this has all been filled out, select the 'App features' tab and then 'Personal App'. In the popup enter your Halo portal URL in the 'Content URL' field as well as a name to identify it.
Finally, press publish and select 'Publish to your org' which will allow users in your organisation to make use of the App you have created. You can also preview the app in Teams before publishing to ensure that everything is set up correctly.
Once complete you will be able to access your Halo portal from within Teams.