Log in to your RIO account and navigate to Fleet Administration via the main menu.
In order to be able to see the position data on the RIO map, you still need to book the appropriate service. In this case it is Geo L, which you need for every truck. In addition to the familiar Geo features, the costs also include all costs that arise from the connection of your external account.
Check everything again for correctness and then confirm the booking. Now* you can see your trucks in the fleet monitor and start working on just one map.
*Here several systems work hand in hand and exchange large amounts of data. Therefore, in some cases it may take a little while until you find your vehicle on the map for the first time. After one hour at the latest, everything should fit.