HelloSign for Confluence requires at least a Silver Tier subscription which grants OAuth and API Signature Requests. Any users planning on making API requests must have a Developer or Admin Role on their HelloSign team. This allows them to create signature requests using the app. To make these changes you must be a HelloSign Admin. Login to HelloSign and go to your settings, then under the Team tab you will have options for each user as seen below.
Additional information on HelloSign Roles can be found here.
Click here for more on HelloSign API pricing.
After installing and licensing the HelloSign for Confluence Plugin, you will find the HelloSign Admin section in the Confluence Administration left-side menu. You may have to refresh the page after plugin installation.
Clicking on the "HelloSign Settings" link will take you to the configuration screen that Confluence administrators can edit.