Theres 2 ways to add/assign licenses to users.
AUTOMATIC METHOD (Highly Recommend)
Remove the old user via the Console. The license will automatically be available. Get the new user to sign in to OWA/New Outlook. The license will automatically be reassigned to the new user.
Step 1: Log in to the Standss SendGuard Management Console
Step 2: Click Manage
Step 3: At the bottom of the screen, remove the user you wish to remove.
You will automatically have that license available to re-assign.
Step 4: Make sure the First come first served button is enabled. This will allow the available license to be assigned automatically.
Step 5: Once the new user logs in to OWA or New Outlook, the license should automatically be re-assigned.
MANUAL METHOD
Step 1: Log in to the Standss SendGuard Management Console
Step 2: Click Manage
Step 3: At the bottom of the screen, Add User(s)
Add in the new users email address and the license will be assigned.