2 answers
Hi Mamta,
Approval Process In Trailhead:-
This approval process, called Approval for Package Deal, is available whenever the opportunity stage is Awaiting Approval, and it assigns approvals back to the opportunity owner. If the opportunity owner approves the discount, the opportunity record’s stage is set to Scheduled. Otherwise, set the stage to Negotiation Rejected.
I get it that you can create an approval process and trigger it using Submit Approval button but it is mentioned that they want the approval to be AVAILABLE whenever opportunity stage is Awaiting Approval. This clearly shows that they want it to trigger automatically from Process Builder where Entry Criteria will be "Stage Equals Awaiting Approval".
Let me know if you need further clarification.
Thanks