You will need to obtain a translator before it is possible to get this one. Trying to interrogate without a translator just means you won't understand the reply given and therefore no trophy.
You will get a Side Op to obtain a translator very early in the game. I noticed it after doing 2 or 3 story missions. Once you complete that side op, you can then complete a successful interrogation for this trophy.
There are 2 ways to do a translation. One is to hold up an enemy that is unaware of you This is done by sneaking up behind and point a gun at them.
Note that if you get seen by the enemy and have to tranquillise them or knock them out then you can press R2 to punch them which will wake them up. Once they are woken up you can point your gun at them.
You then just hold L1 to get the interrogation options.
The other way is pretty much the same, but you hold R2 to put them in a choke hold, then press L1. The choke hold doesn't require them to be held up.