Q.I Left The Flowers On My Big Leaf Hydrangeas Over The Winter. What Do I Do With Them Now, And What And How Is The Best Time To Trim
them. Right now leaves are starting to come out.

Certified GKH Gardening Expert
You can trim off the faded blossoms but make sure you don't cut off any flower buds. You should be able to see them behind the spent blooms. Do not do any pruning till after these have bloomed or you will sacrifice this year's flower heads. Here is more:
https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/mophead-hydrangea-care.htm
https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/deadheading-a-hydrangea.htm