You can enable the mashup ui by executing
ConfigEngine.sh|bat deploy-portal-mashup-ui -DWasPassword=was_password -DPortalAdminPwd=portal_passwordtask. After enabling mashups restart the portal and now when you login you should see My Mashups link on the top next to Home page like this
If you click on the Mashup's link it will take you to Mashup's page which looks like this
You should be able to add iWidgets to this page and wire them to each other.