In the Bosma app, go to Device Settings -> SD Card. If the SD card is recognized, you should see a pie chart of its available and used storage space, and you should also see a “Format SD Card” option at the bottom.
If your SD card is not recognized, the page will show a “No SD Card” text. Please check whether you have correctly mounted the SD card in the device.
Note that Bosma devices support a micro SD card up to 128GB, and it must be formatted in FAT32 (you can use your PC to format the SD card to FAT32). If you inserted an SD card while the device is powered, you would need to restart (power off then on again) the device for the SD card to be recognized.
If your SD card is still not recognized, please try another SD card if available, or contact customer support.