Step 1: assemble spine and head.
Step 2: assemble lower pelvis and legs.
Step 3: assemble pelvis halves and add hips.
Step 4: Add transverse processes from largest to smallest towards the end of the tail.
Step 5: Add largest rib (with the arm sockets) at the third slot from the neck (#1). Then alternately add ribs on either side from largest(#2) to smallest(#6).
Step 6: Glue claws to the heel slots
Step 7: add arms and glue gastralia to the bottom of the largest ribs (They float unattached to other bones in the real T-Rex skeleton). Give yourself a reward. You did it!