You might suggest that if they don’t know such things then they shouldn’t be dating, but that’s probably just a semantical issue.
But I also want to encourage them to move slowly, be careful, and relax.
They should be moving slowly and simply building a relationship that may or may not go anywhere.
It’s not that just dating around for fun is appropriate for Christians, I am certainly not intending to communicate that.
The young Christian couple dating are not essentially married.
Their relationship does not, in any way shape of form, mirror the ancient custom of pre-marriage (where an engaged couple was essentially married but had not consummated their marriage, see Mary and Joseph in the gospels to get a picture of this).