The Nebra indoor unit does not include the 4g module and can be purchased separately here.
Location of where the 4G module and the SIM Card needs to be attached.
Get 4G module and push into slot
Push down on module so it clicks in .
After the module, you'll also need to screw in the antenna connector. The software would be fairly simple, you remove the Compute module board and plug it into your computer with USB. Run a piece of software that makes it act like a USB drive. Copy a file over and then unplug, put it back into the hotspot and you're set.