Thank you for your question, Catherine.  I'm not sure this is a horticulture issue.  If you are wanting more blooms on the same stem, you need to leave a bud.  But you may not be able to tell whether a leaf or a flower bud will grow there.  And some hydrangea varieties do not bloom more than once a year.  Perhaps the following will give you some help:  https://extension.oregonstate.edu/gardening/flowers-shrubs-trees/general-care-hydrangeas

Good luck!