Any TnT that you place or is within your vicinity will detonate automatically. The way it works is relying on beetroot seeds to replace the TnT and summons an ignited TnT in it's place, so keep in mind that beetroot seeds have more than one feature now if you drop them, they were chosen as a detonation mechanic because it is the least of use to players. You can place it anywhere and it will ignite (except in water because water stops collision damage). 

Most of the time the addon is activated by default if you install it in a world, but if it happens to not be working then just type the command "/function tnt/tick" to start it. You can use it for any map or idea you want just like tnt jumping.