Setup Xbee S2 only with only "minicom"

I want to setup two Xbee with raspberry pi. Therefore, I used “minicom” to Tx/Rx the serial from/to Xbee. I succeed to follow the command line setup instructions (such as ATID, DL, DH), and receive “OK” from Xbee. However, I cannot transfer text between them after setting.
Does anything I miss? or I can only use Xctu?

Is one of the module loaded with Coordinator firmware. Only a coordinator can initiate a network.

If not, use XCTU and XBIB dev. board to load ‘Coordinator AT’ firmware on one module and ‘Router AT’ on another.

Thanks. I need to load the coordinator’s firmware first.