To register an offer on behalf of an Agent, go to the specific Listing > Click the Appointments Tab

Look for the Showing Agent name that would like to register an offer for. Below  the agents name there will be 2 icons that you will see, the Letter Icon is for Registering an offer for an agent. Envelope icon is for messaging the Showing Agent directly. 

You can also register an offer by selecting the Offers tab at the top of the listing options


You will be prompted to enter the following information