Overview

In order to create a Fax Portal, you first must enable the Tenant Portal. You can read about that here:
https://support.skyetel.com/hc/en-us/articles/360041180153-Tenant-Portal

Once you have created your Tenant Portal, follow these steps to make a Tenant User that is able to only access the Fax features on their account. 

Create User and Assign Permissions

Navigate to Tenants -> Users:

Once here, click Add Tenant User:

Now, you have to complete the user information and assign permissions only for the Fax features:

Lastly, simply add the fax numbers that this Tenant User should have access to:

If you don't see any phone numbers to select from, compare your DID configuration to the example below:

That's It!

Now that you have created this user, they are able to sign into your Tenant Portal and send/receive faxes only on the number(s) that you specify.