Furious Trophy in Iron Sea Defenders

Before each wave starts, there is a brief timer that counts down. You can use this time to place or upgrade your towers.

You can also bypass the timer, and launch the wave manually. This gives you a small gold boost, and starts the wave immediately. To manually launch a wave, press on PS4 or on PSVita.

Note that the trophy description is rather vague and misleading - there is no Level with 100 waves, and it isn't clear what a 'map' refers to.

I would suggest using this from the start of the game, and it should come naturally. If you are not getting it, start a Campaign from the first Level, and use it on every wave until it pops.