Entering rates for an Agent is identical to entering a Default Rate. You simply go to SETUP | RATES | DEFAULT RATES and click Add to start a new Rate.
Then, give the rate a unique name for example, Agent1, and then write in the value of the rate for a daily, weekend, and weekly value.
Once the Agent1 rate has been saved, you will use it when booking rooms for Agent1 and you will use it as the online rate for your Agent1 when they book from your website(s).