Under the Buckets heading on the left click the icon
Under the Add Bucket heading on the right specify the bucket details
On the Tiers tab click on the + New button and populate the following fields:
Flat Charge: the value entered in this field will be charged when the tier is reached. If a flat charge is configured on the 1st tier then any amount usage applicable to the bucket (e.g. 1 byte of usage against a data usage bucket) will cause the tier to be reached and the flat charge applied
Threshold: specifies the size of the tier (unit options listed here are determined by the base bucket's Unit Type). E.g. for a data bucket you would enter a Threshold of '10' with a Unit of 'GB' to create a tier ten Gigabytes in size. When the threshold is exceeded any flat charge and rates setup on the next tier will be applied. If there is no higher tier to use, and the last tier is not set to repeat, then rates in a rate plan will be used to calculate usage charges (the lowest level rate plan found will be selected if multiple rate plans are found). If no rate plan can be found the rating engine will generate rating exceptions when processing usage data related to the service
Click Add when finished populating tier details. Repeat the process to add additional tiers if desired
When you have finished configuring the usage bucket click Save
See the services help guide for instructions on adding usage buckets to services in the product catalog.