How can we Assign Lead Automatically on basis of "Source" After Assignment Rules are Configured ?

New Leads are generated from Eloqua automatically in Sales Lead. In all that Lead "Source" is configured as "Eloqua" and we have also configured that if Source is "Eloqua" it should get assigned to one specific Employee. We did all this via - Manage Sales Lead Assignment Rules & Manage Sales Lead Assignment Objects.

But it will only work when someone will Manually Click on "Run Assignment" button on Lead Profile Page in "Actions" on Header.

What we want is once Lead is created in Sales Fusion with Source - "Eloqua" Without manual Intervention it is Assigned to Specific Employee.

How to Achieve this ?