Land your hammers. Easy. Just run around hitting other heroes with hammers any chance you get. This will just generally piss them off and add damage to your hammer thanks to Perfect Storm.

Stick with others on your team, your manage won't be the best at this point in the game so just try to land some hammers to help get a kill and make sure you save your E to either finish a kill or escape. Try not to spam your W too much, unless it will finish a kill or clear a minion wave. It's also good at this point in the game to help your team push when you can; you can do a decent amount of siege damage.

Go ham. When you have mana, which you should by this point in the match, throw your hammer whenever you can in team fights; make sure you target the appropriate hero though. At this point you should also be pushing whenever you can with your team, and if it seems like an okay time, don't be afraid to solo any merc camps.