How do I configure carrier aggregation on the WAH7706 (LTE4506)?

You don't have to configure carrier aggregation on the WAH7706 (LTE4506), since it is enabled by default.

However, it doesn't mean that the WAH7706 (LTE4506) can always be carrier aggregated.
Whether the WAH7706 (LTE4506) can be carrier aggregated depends on the network connected to it. Not all ISP are supporting it.

When the WAH7706 (LTE4506) is carrier aggregated, you can see a "4G+" icon on the upper left corner of the WAH7706 (LTE4506)'s web GUI. When the "4G+" icon is present, it implies:

1. The WAH7706 (LTE4506) is carrier aggregated.
2. The downlink speed is higher than 10 Mbps.
3. Data is transmitting.