You can "get married" in a humanist ceremony -
What is a humanist wedding?
The bride and groom together with the celebrant establish what elements they would like to include in the ceremony this special day for them. May freely choose together words, music, gestures and symbols through which they would like to tell us about yourself and the relationship that unites them.
Marriage is a humanist, because everything is directed at the man.
Through the humanist wedding two people expresses the social community their INDIVIDUALISM. They express in it its own aesthetic, their views and desires. It could be something deadly pathetic or extravagantly humorous. Humanistic ceremonies may amuse, shock and delight.
They impact on the emotions and the intellect. Their shape is always a matter of taste of young couple, which of course is not always the taste of all gathered.
Frankly speaking, it's complete nonsense - it has no legal value and is not registered anywhere. You could just as well hire and actor. You could just as well buy a ring and call each other husband and wife without bothering with any ceremony, to the same legal effect.
No official or priest is going to marry you without the paperwork.