Hi Manish - suppliers are enabled via standard account in the SAP Digital Supplier Network (DSN). This process is self-service for a supplier, and the registration usually occurs once an electronic PO is sent to them for the first time from your customer.
As an implementation partner, we recommend you cover at least the following in your project:
1. Develop an Enablement Strategy for your Customer
2. Develop a Communication Plan for your Customer
3. Educate the Customer to do it themselves
SAP provides the Supplier Enablement Tools & Resources to facilitate the process. Sometimes a partner includes the enablement of 5 or 10 or 20 of the most strategic suppliers with their customer in the SOW too. Call it on the-job-training.