How to make a walkie talkie from a radio?

A walkie-talkie is a hand-held, portable, two-way radio . This type of radio, also called handy talkie, handheld transceiver or HT. It’s allows to talk on the radio while walking around, hence the name walkie talkie.

Radio is the technology of using electromagnetic waves of radio frequency to carry information such as sound.

.

Difference between   a walkie-talkie and a radio(Uniden PRO505XL CB Radio) is that a radio is one way communication and a walkie-talkie is a two communication device, now this implies that each walkie-talkie has a radios transceiver.  But walkie talkies and two way radio are the same thing. The terms can be used interchangeably but because they’re often marketed in different ways, walkie talkies are sometimes thought of as a more basic product, promoted as a child’s toy, or used by hobbyists and business users with simple radio needs

Now if u have a two radio transmitter and receiver as two separate units u can mount the transmitter and receiver on one board. Now we need to know if we have to transmit or receive at any given time, for this we can use a simple micro with some basic logic and some start stop  signal to tell the micro if it has to "listen" or "talk"

The logic would be something like this 

StartListning(); // initialize the receiver
If buttonpresd = 1{ // check for the push but ten state 
StartTalking(); // initialize the transmitter 
}
Else{
StartListening(); //revert back to listening 
}

Now this is a very broad over view and u can build upon this by adding things like a condition that if one is transmitting "talking" the other cannot go into transmit mode 
Do you know more about Portable CB Radio

YOU can also achive the same result by replacing the  micro with a simple switch logic but you can't add certain features like avoiding both units being in "talk" or "listen" mode.