Hi Tracey
Seaweed is great as fertiliser but don't expect immediate returns as it takes some time to break down properly.
First off rinse it thoroughly to get rid of any salt. then you want to shred it as fine as you can manage/be bothered. Where you feel you have particular trace element problems around established plants it can be used as a top dressing/mulch. It will really enrich your compost if mixed into that or it can be dug directly into veg beds when preparing - best done late in the season.
Hope this helps and sorry it took a while to respond.
Richard