The fun of inserting in sideways is way too different than from front or back. The man becomes capable to stroke her in those rare places not usually reached.
Steps to perform:
Step1: The woman lies on her back with her arms and legs are spread sideways.
Step2: And one leg is bent in the knee.
Step 3: The male partner lies on top of her a little diagonally.
Step 4: This allows his opened and straight legs under the bent leg of his female partner.
Step 5: He holds the weight of the upper body on both arms (like pushups).
Step 6: Then the man inserts his penis into his female partner sideward.