If you're going to do what Irv said, you have to put a 200A panel in with a 100A breaker in it and run wires from that 100 A breaker to the main breaker on your existing panel. You can't just take the 200 A feed wires and connect it to two boxes.

You can't go around it. You must replace the panel or at least add a 200A and use the old one as a sub panel.

Also, are you "converting" this yourself? I sure hope you called your electric company to upgrade the service drop and you're not just putting in a 200 A main breaker on a system rated for 100 amps. If not, please tell me you at least don't live near me. I don't want my house burning down from your stupidity.

The power feed from the light-pole to the house must be changed first. A 200 power feed requires a ground post buried four feet in the ground outside the foundation.

Basically you can't.

You CAN install a 200 A. service and use the existing 100A.

panel to distribute part of the load via a sub-feed.

The old panel can re-use it's main as protection for that panel.

Any added loads go on the new service.

Ummm.... Change breaker switch and fuses? Check local codes first.

Just splice it in and buy a new fire extinguisher. Have someone on watch 24x7.