Once you have subscribed to a Professional or Business plan, you'll want to set up your account. To utlize SignRequests API, you are required to be subscribed to the 'Business' plan.
The first things you'll want to do are:
1. How to start a free trial?
How to start a free trial?
2. Create a team
3. Invite your other users (if applicable)
4. Create templates
5. Send your first SignRequest
6. Managing sent documents
The following video restates the above: