how do i program an rf t/r pair?

hi! i’m using 3 rf klpa pairs and i need to give each pair a unique ID so that they’ll be able to recognize who sent message and who message is for… i only used a max 233 level converter for the hardware… 2 of the pairs will be connected to hc11 microcontrollers while the remaining pair will be connected to the computer’s serial port… how do i program them? please help!!! thanks!!!