Configuring Multi-Tenancy in SharePoint 2010

Create a SubscriptionSettings Service Application and Proxy

Subscription settings service application is used to keep track of Multi - Tenant services and subscription ID's. So go to the below path

Start the  Microsoft SharePoint Foundation Subscription Settings Service

Central Administration => Application Management => Manage services on server
Start the service "Microsoft SharePoint Foundation Subscription Settings Service".

Create Service Application and Proxy via PowerShell

 $appPool  =  New-SPServiceApplicationPool -Name Subscription_Settings_Service_Pool -Account Domain\UserName

$sa = new-spsubscriptionsettingsserviceapplication –Name SubscriptionSettingsServiceApplication –Databasename SubscriptionSettingsServiceApplicationDB –applicationpool $appPool

$sap = new-SPSubscriptionSettingsServiceApplicationProxy –ServiceApplication $sa

Create Tenant Administration site

New-SPSite –url "http://<servername>:<port no>/sites/Tenant Administration" –template "tenantadmin#0" –owneralias Domain\UserName –sitesubscription $subscription -AdministrationSiteType TenantAdministration

Create Member Site

Before creating the Member\Tenant Site enable the Self Service Site Creation of the Web Application.

Click Manage Site Collection under SharePoint Site Section on the Tenant Administration Site

Click New  and enter the required information  then click ok.

Reference : http://blogs.msdn.com/b/russmax/archive/2010/04/03/sharepoint-2010-multi-tenant-hosting-part-2-configuring.aspx