# It came about

This phrase is used here to mark the beginning of a new part of the story. 

# it was told to Judah

"someone told Judah"

# Tamar your daughter-in-law

"Tamar, your oldest son's wife"

# she is pregnant by it

"it has made her pregnant" or "she is pregnant" 

# let her be burned

"we will burn her to death"