The top is worked flat in two pieces (front and back) on circular needles starting from the bottom with some waist shaping and bust darts.
The pattern repeat is quite wide, so if your body measurements fall in-between two sizes (or outside of the available sizes), try to resize it using different size needles. Please keep in mind that you can resize it only to a certain degree (e.g. make XS out of S), but if you need to make e.g. 2XL, you should recalculate the whole pattern by adding one or two additional repeats and adjusting the darts.

This pattern does not contain any step-by-step instruction: the pattern is charted for sizes S, M and L. If you are a moderately-experienced knitter, you will have no problem following it. The only thing you need to know is how to knit short rows using shadow wraps, but there are lots of YouTube tutorials for that.