Remote explosives are some of Hitman’s most potent killing devices, though they can be fairly tricky to find in some levels. Since the remote explosives are roped off until you receive a level 20 mastery, you will need to acquire these devices out in the world. Thankfully, they are only located in a locked off armory surrounded by dozens of armed guards, easy right?
In order to get these explosive devices, I would recommend either obtaining a guard uniform or one of the propaganda creator outfits. Both will allow you access through the checkpoints and give you enough breathing room to move without being seen. Also, make sure to bring a lockpick, as you will be entering through the side door to avoid suspicion. Make your towards the school where Reza is held up and head towards the front right of the building. Located on the first floor, you will be able to tell which room it is by the guard standing in the doorway.
Make your way back up the hallway and enter the open room next to it and proceed to pick the lock to the double doors. Enter the room and your lovely hitman can find four remote explosives on a table near the window. Also in this room is an assortment of ammunition and various weapons in case you were planning to go the less subtle route. Just make sure to play responsibly with those explosives! Who knows what damage you could cause with them.