If you are using the original Monimoto SIM card that came with the device and the app HOME screen looks like this
You just have to go to the Monimoto app > Settings, press TOP UP SIM CARD and you will be linked to the shop monimoto.it where in just a few clicks you can TOP UP your SIM card.
If you can't find the SIM CARD menu on your app and on the bottom you see [V1], it means that your Monimoto is running on an old cloud version and the firmware needs to be updated. Just visit the dedicated page monimoto.com/new and update firmware to the latest version. Once the firmware is version 0.10.5.61 or later, it automatically applies to the new cloud [V2] and you can see the TOP UP SIM CARD menu.