How can I get Sales Order from R/3 to CRM

I want to know how to transfer the sales order from R/3 to
CRM, and how to bill for that particular Sales Order such
that it replicates in R/3.
My Scenario is:
I have to get the Sales Order from R/3 and I have to bill for
that particular Sales Order in CRM and this bill document
has to replicate R/3 also.
✍ ANSWER
Billing does not replicate from CRM to R/3, but the financial
data will transfer to R/3 F/I (just no invoice in VF02, VF03).
To transfer the order it has to be configured in both systems
and middleware parameters set up.