Before practising the arm drag technique you should master the arm-drag drill.

Arm drag drill

As your opponent places his left hand on your right shoulder, pat his extended arm with your right hand, catch his arm with your left hand and drag his captured arm to your left side. While pulling his arm, step forward and cut your opponent off. You don’t want to step where he was. Instead step where he will end up after pulling on his arm. Your opponent will go right into you, allowing you to tie up and take him down.

It’s very important to cut your opponent off to stop him from redragging and denying you from the position you were looking for.
Try to master this skill on both sides.

Another more effective arm drag drill where you have to break your opponent grip by bringing your arm up into his arm and then circle your arm toward the outside of your body. Once you’ve broken his grip and forced your opponent’s arm from your body, circle his arm back and feed it to your opposite hand so you can execute the arm drag.
Try to master the drill from both sides.

If your opponent has gained control of your wrists, you should punch your trapped hand down, straightening you arm then reach with the other hand across your body and latch to his upper arm. Your palm should be capped around the inside of his biceps and your fingers should be clasped around his triceps.

If you have gained control of your opponent’s both wrists, start by forcing his right arm down toward your hips using your left hand and then hook your right hand around his right triceps. Your palm should be cupped around the inside of his biceps and your fingers are clasped around his triceps. Pull your opponent’s arm to your right side and use your right hand to force him to step his left leg across your body in the direction of the drag. While doing this step your right leg out at a 45 degree angle to cut him off. As your opponent moves into you, wrap your left hand around his back and latch on to his far hip to complete the take down.

When your opponent prevents your from obtaining and under hook by keeping his arms pinched tight to his body, reach your opposite arm across your body and latch on to the arm his blocking your underhook with and then arm drag him to follow with the take down.