It depends on the QR code on the HomeBase or indoor cam. If there is no Home logo, it means the camera/HomeBase cannot be added to the Home app directly. 

If there is a “Home” logo, follow the instructions on the Home app to add accessories. Here is an Apple support article for reference. https://support.apple.com/en-hk/guide/iphone/iph125110541/ios

If there is not a "Home" logo as above, please refer to How to Setup HomeKit for HomeKit-Enabled Security Devices for detailed information.

Note:

The HomeBase with home logo has been discontinued. At present, the HomeBase sold in all sales channels does not have a home logo. But the method in this article is still applicable to HomeBase with home logo printed.