Deploying or publishing is where segmentation is most often applied. To segment a list when deploying a campaign, go to TASKS > DEPLOY CAMPAIGN. On the first page of the wizard, make your selection for Normal mailing type, select the List, Template, and Segmentation Rule and then continue through the wizard, as described in Deploy Normal Campaign.
The default segmentation option is 'All subscribers', which is no Segmentation Rule. All standard, advanced, event based, and n-way segmentation rules are available to select. The last page of the wizard will display the number of subscribers that are on the list. Click UPDATE COUNTS to view the results after Segmentation is applied.