Once you have the reseller id you would first call the pairTerminal() method of the api which will return an API Key/Pwd and terminalID which you would store on your end.
You would then use those credentials with the runTransaction method to run a sale. Please be sure to read the area on the pairing page as it describes the importance of the referenceID when calling the pairTerminal method.
All commands require a key, pwd and terminalID parameter which is obtained from the pairTerminal method.
When complete with the integration, we highly recommend testing your integration with our best practices guide.