You can select a token from the token inventory, then assign the token to a user.
Navigate to the token inventory
If you know the token's serial number, then enter the serial number to find it
Click the token's actions menu, then select "Assign"
Select the directory, aka the Identity Source, in which the user is to be found
Find the user by name or email address
Optionally, you might want to enter an OTP code generated from the token to make sure that you have picked up the right token
Tick the "Activate Token" option if you also want to activate the token at the same time
