Question: How do I screw the 5" decking screw into the beam ?
Options:
With a power-drill drill a 3/8 in hole 3 inch deep into the beam, then screw  the screw into the hole with a ratchet.
With a power-drill drill a 3/8 in hole 3 inch deep into the beam, then screw  the screw into the hole with a hammer.
Answer: With a power-drill drill a 3/8 in hole 3 inch deep into the beam, then screw  the screw into the hole with a ratchet.