I need a feature, admin to add and process orders for clients.
have you discovered Act on Behalf of - in Sales > Customers?
It allows you into an existing customer account to add, change, etc an order.
If customer does not have an account you will need to make one for them.
see image for how to get there:
as for processing, you can control that by how you handle the status of an order - see order status for selections, and you can add any additional status points you may need.