There are two basic ways regardless of how many nodes you have.
Both use the same basic configuration of a Point to multi-point network topology
Base Remote
MY0xFFFF MY0xFFFF
DL - SL of desired remote DL - SL of base
DH - SH of desired remote DH - SH of base
The first is to use transparent mode Entering command mode and changing the DL/DH to match the SL/SH of who you want to send the data to. Exit command mode and then send the data. Continue doing this till all nodes have communicated.
The second is to use API mode on the Base which then allows you to use a known API frame that allows you to send the data to which ever 64 bit address is listed in the API frame. No need to enter command mode so this is the fastest rout. In this case, you also get to know who send the data to the Coordinator where as with the first option, you need to have some sort of address within your data payload if you want o know who sent it.