I have assigned someone to the gun and gone to the marked gas station test target and I equip the smoke and when I try to toss it all I do is throw a punch I noticed that I can have a weapon selected at the same time as the smoke so I tried that but that just shoots the gun.

Equip it and throw like any grenade. R1 ps4

Have the smoke grenade as your 'equipped' grenade, then toss a grenade as usual. Default on PC is hold left Alt button, then release to throw the grenade.

Thank you I had totally forgotten it was the left alt .