For plugin to work with 1-Stream panel you need API Key and API token.
API key is created by admin in panel.
If you are admin then create API key yourself, if you are reseller then ask from admin.
API token is created by reseller in panel.
If you are reseller then create API token yourself, if you are admin then create reseller account and login as reseller to create API token.
API key:
Navigate: Settings->API Access Tokens
Click: Add API Access token
Input: Fill required fields
Click: Save
Click: Key icon to show created key
API token:
Click: Your username upper right corner.
Choose: Profile
Click: Create token
Input: Fill required fields, add permissions (showUserProfile,indexPackages,createLinesWithPackage,destroyLines,statusLineToggle,indexSubresellers,editSubresellers)
Click: Create
You can also read about API access on official website of 1-Stream: https://billing.1-stream.com/whmcs/index.php/knowledgebase/12/Billing-Addon-3rd-Party.html
Save API key and API token somewhere (keep them safe!), you will need them in plugin configuration in aMember.