Time out help

Ok.. I think we need to start time outs for my 4 year old. I have some questions though.

Lately she’s been having meltdowns screaming so loud that are scaring her 7 month old sister

How do I go about doing this with her? There is no way my 4 year old would sit on a chair when she’s in that mode without being constantly picked back up to be sat back on the chair. But if it’s already that bad I need to put my older daughter in a time out, what do I do with her baby sister when there is no one else home besides us? Bc I’m constantly going to be needing to pick big sis up to place her back on the chair and I know she will be screaming at the top of her lungs during this.. but her baby sister will be scared from big sister yelling and I want to comfort her during it and keep her distant from her sister. Our house is small so another room won’t really make a dif from hearing the yelling. I should’ve started time outs a couple months ago honestly when her behavior started getting worse at times, but I thought doing a time out for big sister would also be like a punishment for little sister bc I know big sister is going to scream at the top of her lungs and scare little sister the whole time

Also - I know 1 min per age they say is a a good time. But is 4 mins too long for doing this for a first time with my 4 year old? Maybe 2 min is better for first few times?

Any other advice? Paren