Help with understanding pattern instructions

[mel.b]

Hi,

I'm about to pick up the needles again after a break of almost two years I've got a pattern by Sirdar for a Jacket (pattern number 9170 I think). Most of it is straight forward, however it has this below which has confused me a little...

using D working in st-st(throughout) work 24 rows more
Cast off loosely
Using A work 7 of Square 1
Using B work 8 of Square 1
Using C work 10 of Square 1
Using D work 6 of Square 1

Now I understand the first two rows(!) but the next four rows have me a little confused. To start with, how do I 'work them'? Do I have to pick up and knit from the cast off or something else?? And do I continue in st-st or just plain knit?

Any help would be great!
Mel.b