# They went in to her, as men go in to a prostitute

They had sexual relations with her in the same way that men have sexual relations with a prostitute.

# They went in to her

"They went in to where she was" or "They went to her"

# In this way they went in to Oholah and Oholibah

"This is how they had sexual relations with Oholah and Oholibah"