Several things off the top of my head:

1) How do you throw grenades/Molotov's? Have YET to figure this out. Followed on screen instructions, did nothing.

2) Using workbenches....can't build anything. Must level or a certain skill be at a certain level first?

Have to hold the melee button for about half a second, till you hear a ping like a grenades spoon/handle releasing. Then you'll toss. But first make sure you have a grenade type selected in inventory first, otherwise nothing'll happen.

And make damned sure you're aiming far enough away that you're out of the blast radius. If that explosive bounces back at you you're in for a bad time.

Stupid Molotov Coctails.

I honestly think the way they've done grenades and explosives in general is just counter intuitive.