About the one you will leave in the pot. follow the directions below---if it will not fit on the sill, place it on a box or something so it will be up high enough or far back enough to get some sun from the window.
Try to do it this way:
1) bring it in in a pot...
2) Prune back the stems by 1/3 but do not take off too much.
3) water thoroughly 1 time a month.
4) Place it in bright, but indirect light. or you can place it under a grow light for 10 hours a day if no such light is available.
5) keep it in a cool dry place.
6) Place it out next spring
or you can even plant it out in the soil then, but next fall you should take more care when digging it back up, so as to disturb the roots as little as possible.
7) after you have had it back outside for 2 weeks,
caring for it as you have in previous springs/summers...you can cut back the dead and or leggy pieces.