I've done the Einstein coat, but it's been years.
My best suggestion is to look at the picture. The bottom runs with the ridges in one direction - I think up and down. So turn your already-knitted bottom to the same direction. Put the two edges that'll form the front opening towards you. Now look at where you need to put the front top. It'll be starting at one of the opening edges and gets knitted from stitches you'll pick up along the side of your knitted bottom - the side that starts at the opening and goes to about where the future armhole will be aligned with... in other words, about 1/4 of the bottom.
Hope this helps. A hint: when picking up stitches, mark the beginning and end of the portion of the existing edge that your stitches must cover. Now fold the two markers together and put a 3rd marker - this is the half-way point. Now divide the # of stitches you need to pick up by 2 - and you now can more easily gauge the spacing for your pick'em-up stitches: half on one side of your middle marker, and half on the other side.
If you're dealing with a huge lot of stitches to pick up, then divide the halves in half again.
Hope this helps,
My words sell the Magic of a Dream