A couple Questions on Master Cleanse...

Hello everyone,
I am new to this fast, never done it before..
I was wondering what I am supposed to do on day one.. Should I start with the Lemonade only or should I also do the Salt water flush first thing in the morning? Should I wait with the SWF (Salt-Water-Flush) until day 2 or 3?
And I am naturally underweight. I weigh 118 pounds and my height is 5'9. So I am a little worried about loosing weight - I cannot loose weight! But I really want to do this fast because I got off the birth control pill about 7 months ago and quit smoking about 4 months ago and my body is already detoxing which is very visible in my skin. It's gotten pretty bad and I thought The Master Cleanse would help and speed up the process of getting all the bad stuff out.
I was thinking of starting tomorrow, am really excited, just don't want to loose weight.
Anyone out there with some answers? :)