Hi Haseena,

The employee center tab introduced as part of the integration is oob provided. In case you want to customize, please check the process from Microsoft documentation to add more custom tabs.

https://docs.microsoft.com/en-us/microsoftteams/platform/tabs/what-are-tabs#declare-custom-tab-in-app-manifest

In order to add tab to the existing Servicenow App, you need to build an azure app and make changes to app manifest.json.

Thanks,

Ragu