I know it's probably my age but i can't work out how the two cages swing across the fire pit in the first section

Can anybody help?

Easy first you need to kill the henchmen then cross the lava river but don't switch anything before then when you cross the river then put the powder barrel in the cage and then activate it it will go on the other side then go to your left and swing back get the bomb and then light it up it should blow up the cage activate the switch in there that pretty much what you have to do