This step should be performed by a Tenant Administrator only.
Step 1: Authorization
Upon first use, a permission request will appear. Click “Login to Azure AD.”
Next, check "Consent on behalf of your organization" and click on "Accept." This will prevent the permission request pop-up for each user.
If you don’t receive this alert message, skip this step.
Step 2: Grant Permissions
Open the Virto Calendar App settings and click the "Edit Calendar" icon on the top left.
In settings, you will see a message requiring additional permissions. Click "Grant required permission."
A window with an expanded list of required permissions will open. Click the checkbox and then the "Accept" button.