[HayZee518]

what you would do is remove a double pole breaker in your main and put in a two pole 100 amp breaker. next to the main you'd put in a main lug sub-panel. feed it with #2 copper four wire or #1 four conductor aluminum. Inside the subpanel the neutral would be isolated above ground and an auxillary ground bar would be fastened in intimate contact with the metal enclosure. the bare conductor (ground) would go to the aux strip, the white to the neutral (no bonding screw) and the two hots to the main lugs. Re-route the cable that was connected to the original two pole breaker to your sub panel and install its two pole breaker there and connect up the wires.