You can see the retention policies available to you in Outlook Web App options. In Options, select Organize email > Retention policies. Or, in Options, select MAIL >Automatic processing > Retention policies.
To assign a retention policy to a message or folder, you have to go to your messages.
Sign in to Outlook Web App. Typically, this is webmail.emaildomain.com (IE: webmail.adbinc.com). For addtional help, see Sign in to Outlook Web App.
At the top of the page, select Outlook (or Mail). Or, select the App launcher , and then select Outlook.
In the folder pane, right-click the message or folder for which you want to apply a policy and select Assign policy.
Select the policy you want to assign. You can also select Use parent folder policy. The policies that are available are controlled by your organization.