Here you have some POEMS to see how to write your own one in your card.
Here you can see some examples to make your own Valentine´s Card.
You need to write this inside your Valentine´s Card:
Dear Family/Friend/ Parents/ Grandparents, …..
HAPPY SAINT VALENTINE´S DAY !
FROM: …….. (YOUR NAME)
And then you can write also a POEM or another sentences related to this special date.