Pools are simply a group of agents that you define, which you can use in your distribution rules. To setup a new pool, click the "Distribution" menu item in the left navigation, then choose "Pool Settings"
Next, click the "New Pool" tab then enter a name for your Pool
All the available agents will be on the left under "All Agents". To assign agents to the current pool, drag and drop each agent from the left, over to the right container labeled "Pool Agents". After you have moved the agents you would like in the pool to the right container, click the "Save Pool" button.
If you would like to edit a current pool, from the "Pool Settings" tab, simply click the edit button, drag the agents from the right container back to the "All Agents" container (Reverse of adding an agent to the pool from above), finally click the "Save Pool" button.